rk808: fix deadlock when shutown or reboot

rk808: fix deadlock when shutown or reboot

When shutdown, rk808 driver shutdown first, so io_lock mutex is locked.
At same time, gpu change freq by runtime pm, will locked on rk808_reg_read.
Finally, gpu device shutdown, call pm_runtime_barrier. Deadlock happens.

Fix this bug by make rk808 shutdown later.

  task                PC stack   pid father
init            D c06e9a14     0     1      0 0x00000000
[<c06e9a14>] (__schedule+0x48c/0x554) from [<c02e281c>] (__pm_runtime_barrier+0x114/0x138)
[<c02e281c>] (__pm_runtime_barrier+0x114/0x138) from [<c02e3cf4>] (pm_runtime_barrier+0x68/0xb8)
[<c02e3cf4>] (pm_runtime_barrier+0x68/0xb8) from [<c02d85ac>] (device_shutdown+0xa0/0x190)
[<c02d85ac>] (device_shutdown+0xa0/0x190) from [<c0042128>] (kernel_restart+0xc/0x50)
[<c0042128>] (kernel_restart+0xc/0x50) from [<c00422c4>] (SyS_reboot+0x150/0x1b0)
[<c00422c4>] (SyS_reboot+0x150/0x1b0) from [<c000da00>] (ret_fast_syscall+0x0/0x30)
kworker/2:1     D c06e9a14     0    32      2 0x00000000
Workqueue: pm pm_runtime_work
[<c06e9a14>] (__schedule+0x48c/0x554) from [<c06e9ec0>] (schedule_preempt_disabled+0x24/0x34)
[<c06e9ec0>] (schedule_preempt_disabled+0x24/0x34) from [<c06e8bf8>] (__mutex_lock_slowpath+0x1c0/0x22c)
[<c06e8bf8>] (__mutex_lock_slowpath+0x1c0/0x22c) from [<c06e8c94>] (mutex_lock+0x30/0x48)
[<c06e8c94>] (mutex_lock+0x30/0x48) from [<c02f0dbc>] (rk808_reg_read+0x24/0x5c)
[<c02f0dbc>] (rk808_reg_read+0x24/0x5c) from [<c02f0fa8>] (rk808_dcdc_is_enabled+0x28/0x38)
[<c02f0fa8>] (rk808_dcdc_is_enabled+0x28/0x38) from [<c02a6acc>] (_regulator_is_enabled+0x34/0x40)
[<c02a6acc>] (_regulator_is_enabled+0x34/0x40) from [<c02a6c50>] (_regulator_do_set_voltage+0xbc/0x3e4)
[<c02a6c50>] (_regulator_do_set_voltage+0xbc/0x3e4) from [<c02a7c1c>] (regulator_set_voltage+0xc0/0xe0)
[<c02a7c1c>] (regulator_set_voltage+0xc0/0xe0) from [<c0027b7c>] (dvfs_regulator_set_voltage_readback.isra.6+0x14/0x8c)
[<c0027b7c>] (dvfs_regulator_set_voltage_readback.isra.6+0x14/0x8c) from [<c0027d5c>] (dvfs_scale_volt_direct+0xa0/0xc4)
[<c0027d5c>] (dvfs_scale_volt_direct+0xa0/0xc4) from [<c0027f24>] (dvfs_target+0x1a4/0x1d4)
[<c0027f24>] (dvfs_target+0x1a4/0x1d4) from [<c00273e8>] (dvfs_clk_set_rate+0x44/0x80)
[<c00273e8>] (dvfs_clk_set_rate+0x44/0x80) from [<c02c1388>] (mali_dvfs_clk_set+0x28/0x48)
[<c02c1388>] (mali_dvfs_clk_set+0x28/0x48) from [<c02c01f4>] (kbase_platform_dvfs_set_level+0x9c/0xe0)
[<c02c01f4>] (kbase_platform_dvfs_set_level+0x9c/0xe0) from [<c02c032c>] (kbase_platform_dvfs_enable+0xf4/0x110)
[<c02c032c>] (kbase_platform_dvfs_enable+0xf4/0x110) from [<c02bf908>] (pm_callback_runtime_off+0x3c/0x58)
[<c02bf908>] (pm_callback_runtime_off+0x3c/0x58) from [<c02d2650>] (kbase_device_runtime_suspend+0x24/0x34)
[<c02d2650>] (kbase_device_runtime_suspend+0x24/0x34) from [<c02de738>] (pm_generic_runtime_suspend+0x2c/0x40)
[<c02de738>] (pm_generic_runtime_suspend+0x2c/0x40) from [<c02e25c4>] (__rpm_callback+0x38/0x68)
[<c02e25c4>] (__rpm_callback+0x38/0x68) from [<c02e2658>] (rpm_callback+0x64/0x7c)
[<c02e2658>] (rpm_callback+0x64/0x7c) from [<c02e3210>] (rpm_suspend+0x2d8/0x534)
[<c02e3210>] (rpm_suspend+0x2d8/0x534) from [<c02e3e60>] (pm_runtime_work+0x7c/0x94)
[<c02e3e60>] (pm_runtime_work+0x7c/0x94) from [<c004773c>] (process_one_work+0x29c/0x458)
[<c004773c>] (process_one_work+0x29c/0x458) from [<c0047a8c>] (worker_thread+0x194/0x2d4)
[<c0047a8c>] (worker_thread+0x194/0x2d4) from [<c004cf74>] (kthread+0xa0/0xac)
[<c004cf74>] (kthread+0xa0/0xac) from [<c000da98>] (ret_from_fork+0x14/0x3c)