msm_mdp: Update header for 4 layer support

Bug: 7626586
Change-Id: I37730470dc09b7a9d6336b1603f87efd98f45e97
Signed-off-by: Iliyan Malchev <malchev@google.com>
Merge remote-tracking branch 'google/jb-mr1.1-release' into jb2-EXP

Conflicts:
	libc/kernel/common/linux/msm_mdp.h