mdss: enable content adaptive backlight control (cabc) for find7 variants

the original vendor code allows for PWM control of backlight in its own
mdss driver but for some reason the cabc control was hardcoded to use level
3 only for HW revision > 20 (find7 variants).

Re-enble the cabc and pwm backlight control for find7 variants and clean up
the coding style to conform to Linux kernel coding standards as well.

Change-Id: I8bd2fe2d595edd67dedd7e536225fbfc7d5ca3a9
Signed-off-by: Paul Reioux <reioux@gmail.com>
msm: mdss: add real time debug log

To analyze issues like underruns and other timing issues
add xlogs. Add debugfs entry for xlog to enable or disable
logging and register dumping at run time.

Enable xlog: echo 1 > <debugfs>/mdp/xlog/enable

Enable register dump:
echo 1 > <debugfs>/mdp/xlog/reg_dump

Enable panic on error:
echo 1 > <debugfs>/mdp/xlog/panic

Get xlogs and register dump
cat <debugfs>/mdp/xlog/dump

Change-Id: I10c2993d9dde6ef16a37256928fff1239e6370ff
Signed-off-by: Raghavendra Ambadas <rambad@codeaurora.org>
Signed-off-by: Nirmal Abraham <nabrah@codeaurora.org>
msm: mdss: fix race condition of DSI off and status check.

fb_event_callback cancels the work queue when it receives
the power down event. However, this event occurs after the
panel & DSI have been turned off. So if the check_status
function was being called right when the panel is being
turned off, we have a race conditon. Hence add offlock
mutex to ensure that bta status check is done when dsi
is being turned off.

Change-Id: Ie341c002c4544376bda2940fa65c6eb13997ae17
Signed-off-by: Vineet Bajaj <vbajaj@codeaurora.org>