libhwcomposer: Add support for 4 layer MDP Comp

This change extends MDP composition to support
upto 4 layers by making border fill as base pipe and
using all MDP h/w pipes in overlay mode.

Conflicts:

	libhwcomposer/hwc.cpp
	libhwcomposer/hwc_utils.cpp
	libhwcomposer/hwc_utils.h

Bug: 7626586
Change-Id: I01a0e53ddfbcf3ed46734f6f3bb0ef7d912ceac6
Signed-off-by: Jeykumar Sankaran <jsanka@codeaurora.org>
Signed-off-by: Iliyan Malchev <malchev@google.com>
9 files changed