disp: msm: add support for display early wakeup

Display clocks and IRQs are disabled during idle state
on command mode for power saving, and will be enabled
when a new frame commits to display driver. But enable
display clocks and IRQs will cause some latency.
So add a new SDE custom IOCTL for user-space to early wake
up display before first frame commits to kernel.

Change-Id: I6ca0188d321c4964f29c46e588b64d06b9634c59
Signed-off-by: Lei Chen <chenlei@codeaurora.org>