drm/msm/sde: add support for uidle feature

This change adds support to enable/disable microidle feature
in the sde kms driver. This feature allows the HW to increase
the DDR idle time by modifying the fetching patterns during
the active region of display frames.

Change-Id: I812297724ccf37ac65658957e468c0f72876a742
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>