msm: mdss: fix back light issue in recovery

When continuous splash is enabled backlight is
turned on in lk itself. But the pwm_enable variable
is not set till first backlight update in kernel.
In recovery case blank is called even before
backlight update. Since the bwm_enable variable is
not set backlight disable is skipped keeping the
backlight on.

Change-Id: I73c02d8250596e7b6addec4ffc54655bbc8cb53c
Signed-off-by: Ramakant Singh <ramaka@codeaurora.org>