msm: mdss: initialize AD calibration bl to current bl level

When AD calibration mode is turned ON, an ioctl is sent to
set the mode to calibration in driver. However this does not
set the calibration mode backlight. So the backlight value
would remain 0. If bl is not set during calibration then upon
suspend resume the bl will remain as 0 and nothing would
appear on display.

Now initializing the calibration mode bl level to the bl
level when calibration mode was turned on.

Change-Id: Iecee61dc69815b673deb8610a524b07c4f4b9261
Signed-off-by: Krishna Chaitanya Parimi <cparimi@codeaurora.org>