drm/msm: allow SDE HDMI display to support 4K

SDE HDMI driver capabilities were capped
to 1080P due to lack of dual pipe support in userspace.

Relax this restriction as full userspace support to
allow dual pipe support is now available.

Change-Id: If8242ea3c65a901ceb3e1004ac40b29ab8554c4b
Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>