regulator: rk29-pwm: fix sleep in atomic

regulator: rk29-pwm: fix sleep in atomic

fix this bug, only happens when cpu run in 1.2G.
BUG: scheduling while atomic: VideoTrackEncod/414/0x00000202
[<c0431198>] (unwind_backtrace+0x0/0xd8) from [<c079df38>] (schedule+0x74/0x540)
[<c079df38>] (schedule+0x74/0x540) from [<c079f5d0>] (schedule_hrtimeout_range+0x138/0x178)
[<c079f5d0>] (schedule_hrtimeout_range+0x138/0x178) from [<c045bae8>] (usleep_range+0x44/0x48)
[<c045bae8>] (usleep_range+0x44/0x48) from [<c059e010>] (pwm_regulator_set_voltage+0x140/0x168)
[<c059e010>] (pwm_regulator_set_voltage+0x140/0x168) from [<c059d66c>] (regulator_set_voltage+0xe8/0x100)
[<c059d66c>] (regulator_set_voltage+0xe8/0x100) from [<c043f7c8>] (rk29_cpufreq_target+0x5f4/0x6cc)
[<c043f7c8>] (rk29_cpufreq_target+0x5f4/0x6cc) from [<c0671d44>] (__cpufreq_driver_target+0x28/0x38)
[<c0671d44>] (__cpufreq_driver_target+0x28/0x38) from [<c06736c0>] (cpufreq_driver_target+0x44/0x60)
[<c06736c0>] (cpufreq_driver_target+0x44/0x60) from [<c043ec84>] (rk29_cpufreq_aclk_vepu_notifier_event+0x78/0x94)
[<c043ec84>] (rk29_cpufreq_aclk_vepu_notifier_event+0x78/0x94) from [<c046bfd4>] (notifier_call_chain+0x2c/0x70)
[<c046bfd4>] (notifier_call_chain+0x2c/0x70) from [<c046c0a4>] (raw_notifier_call_chain+0x14/0x18)
[<c046c0a4>] (raw_notifier_call_chain+0x14/0x18) from [<c04384b4>] (clk_notify+0x68/0xec)
[<c04384b4>] (clk_notify+0x68/0xec) from [<c04386fc>] (clk_enable_nolock+0x4c/0xc4)
[<c04386fc>] (clk_enable_nolock+0x4c/0xc4) from [<c04391ac>] (clk_enable+0x70/0xb4)
[<c04391ac>] (clk_enable+0x70/0xb4) from [<c0442708>] (vpu_service_power_on+0x48/0xec)
[<c0442708>] (vpu_service_power_on+0x48/0xec) from [<c0442e34>] (vpu_service_ioctl+0x688/0x6e4)
[<c0442e34>] (vpu_service_ioctl+0x688/0x6e4) from [<c04bfa60>] (vfs_ioctl+0x2c/0x8c)
[<c04bfa60>] (vfs_ioctl+0x2c/0x8c) from [<c04c0110>] (do_vfs_ioctl+0x558/0x5c4)
[<c04c0110>] (do_vfs_ioctl+0x558/0x5c4) from [<c04c01b0>] (sys_ioctl+0x34/0x54)
[<c04c01b0>] (sys_ioctl+0x34/0x54) from [<c042bf40>] (ret_fast_syscall+0x0/0x2c)