thermal: rockchip: rk3368: fix bad unlock balance issue

thermal: rockchip: rk3368: fix bad unlock balance issue

We WRONGLY supposed both REGULATOR_EVENT_PRE_VOLTAGE_CHANGE and
REGULATOR_EVENT_VOLTAGE_CHANGE were used in pairs. If volts are
not changed in volts setting process, REGULATOR_EVENT_PRE_VOLTAGE_CHANGE
is NOT sent,but REGULATOR_EVENT_VOLTAGE_CHANGE is sent. So we check the
lock status before we release the lock.

[    3.535657] =====================================
[    3.535703] [ BUG: bad unlock balance detected! ]
[    3.535757] 4.4.55 #2 Not tainted
[    3.535800] -------------------------------------
[    3.535847] cfinteractive/65 is trying to release lock (thermal_reg_mutex) at:
[    3.535969] [<ffffff8008c23ca4>] mutex_unlock+0xc/0x14
[    3.536015] but there are no more locks to release!
[    3.536058] wifi_platform_bus_enumerate device present 1
[    3.536076]
[    3.536076] other info that might help us debug this:
[    3.536088] ======== Card detection to detect SDIO card! ========
[    3.536104] 4 locks held by cfinteractive/65:
[    3.536115] mmc2:mmc host rescan start!
[    3.536123]  #0:  (&policy->rwsem){+.+.+.}, at: [<ffffff8008829734>] cpufreq_interactive_speedchange_task+0x138/0x48c
[    3.536323]  #1:  (&pcpu->enable_sem){++++..}, at: [<ffffff8008829740>] cpufreq_interactive_speedchange_task+0x144/0x48c
[    3.536510]  #2:  (&rdev->mutex){+.+.+.}, at: [<ffffff8008472948>] regulator_set_voltage+0x34/0x90
[    3.536700]  #3:  (&(&rdev->notifier)->rwsem){.+.+..}, at: [<ffffff80080c0558>] __blocking_notifier_call_chain+0x30/0x64
[    3.536892]
[    3.536892] stack backtrace:
[    3.536962] CPU: 2 PID: 65 Comm: cfinteractive Not tainted 4.4.55 #2
[    3.537011] Hardware name: Rockchip rk3368 p9 board (DT)
[    3.537056] Call trace:
[    3.537118] [<ffffff8008088a4c>] dump_backtrace+0x0/0x1c4
[    3.537182] [<ffffff8008088c24>] show_stack+0x14/0x1c
[    3.537249] [<ffffff80083ada90>] dump_stack+0xa8/0xe0
[    3.537317] [<ffffff8008186c04>] print_unlock_imbalance_bug.part.25+0xbc/0xcc
[    3.537386] [<ffffff80080f8210>] lock_release+0x218/0x464
[    3.537448] [<ffffff8008c23c1c>] __mutex_unlock_slowpath+0xf4/0x170
[    3.537507] [<ffffff8008c23ca4>] mutex_unlock+0xc/0x14
[    3.537573] [<ffffff800880510c>] rk3368_thermal_notify+0x5c/0x68
[    3.537637] [<ffffff80080c0248>] notifier_call_chain+0x54/0x88
[    3.537702] [<ffffff80080c0570>] __blocking_notifier_call_chain+0x48/0x64
[    3.537768] [<ffffff80080c05a0>] blocking_notifier_call_chain+0x14/0x1c
[    3.537837] [<ffffff80084701d0>] _regulator_do_set_voltage+0x3dc/0x61c
[    3.537904] [<ffffff80084705b8>] regulator_set_voltage_unlocked+0x1a8/0x208
[    3.537971] [<ffffff8008472970>] regulator_set_voltage+0x5c/0x90
[    3.538039] [<ffffff800850708c>] _set_opp_voltage+0x44/0xa4
[    3.538104] [<ffffff8008508400>] dev_pm_opp_set_rate+0x47c/0x540
[    3.538168] [<ffffff800882be30>] set_target+0x30/0x38
[    3.538234] [<ffffff80088222e0>] __cpufreq_driver_target+0x1d8/0x298
[    3.538298] [<ffffff800882986c>] cpufreq_interactive_speedchange_task+0x270/0x48c
[    3.538360] [<ffffff80080bee1c>] kthread+0xf4/0xfc
[    3.538419] [<ffffff80080826d0>] ret_from_fork+0x10/0x40

Change-Id: I8a89bde9ff6ec83255b8a4c017e6ff792535ebb8
Signed-off-by: Rocky Hao <rocky.hao@rock-chips.com>