msm: mdss: Add support for boot LED indication

By turning on the blue LED we get a notification that the boot-
process has started. The blue LED will be turned-on in
bootloader and be turned off when HLOS display takes over.

Change-Id: Ia8f97a507a5deda9d692f0a8b53488a684f5efd2
Signed-off-by: Shimrit Malichi <smalichi@codeaurora.org>