hwc: Include more cases in partial MDP composition and fix bug.

Fixing bug in partial mdp composition due to layer caching when
UI layer with 90 rotation is present in layer list.

Layer not updating and a layer composed to FB are same now.

When MDP cannot support a layer, we send the whole list of layers to
GPU. If such layers are not updating they can be cached on FB while
allowing the rest to take the MDP route.

Example # 1: Volume bar on video in 90 rotated mode. Since volume bar
is not h/w accelerated, there is no prerotation and we invoke the GPU
for redraws each round. With this change we won't because of caching.

Example # 2: If prerotation is applied to layers on primary, the
secondary layers would show a transform and the whole list is redrawn
with GPU. Now we could make use of caching.

This change also imposes a 1 layer limit on secondary, but now allows
full and partial MDP comp, thus benefiting secondary-only content.

Change-Id: I7eb43ba817f1081f317fefa99fa0c507344060e8

Conflicts:
	libhwcomposer/hwc_mdpcomp.cpp
	libhwcomposer/hwc_mdpcomp.h
Merge "hwc: Include more cases in partial MDP composition and fix bug."
Merge branch 'jb_2.6' of git://codeaurora.org/quic/la/platform/hardware/qcom/display into android-4.3