msm: mdss: restore backlight level when recovering from ESD attack

When ESD related panel failures are detected, the recovery process
involves blanking and unblanking the panel. In such cases, it is
required to restore the backlight level as there may not be an explicit
call from the userspace to update the backlight.

Change-Id: Idd84a628cf2a1e37121b94d3c5cc11d45a78fdab
Signed-off-by: Aravind Venkateswaran <aravindh@codeaurora.org>