hwc: For FB target check RGB pipe availability before VG pipe

If RGB pipe is available then it should be allocated before
allocating VG pipe for FB target.

Change-Id: I0c1f0fd08a7779eb077e9e9c1809bdbcaff2227c
hwc: Disable mdp comp if mDownscaleMode is set for external

If mDownscaleMode is on then scaling will be done. Sending a RGB
layer with alpha to VG pipe can cause composition issues.

Change-Id: I215a5d7360fe741124e809be0b66c328c943d7dc
overlay: Allocate from MM heap as a fallback

 * Not all devices support IOMMU yet, so use the MM heap as a fallback.
 * Enabled when NO_IOMMU is set

Change-Id: I9d9f3dffb92f5b4bf45422df0f66a40611943202
display: Cover NO_IOMMU for msm7x30/msm7x27a too

Change-Id: Ic68672f386a06fd0ac9fd1f18eec3188415a8642
hwc: rotator is not supported on msm7x27a

Change-Id: I26fe237831eb6fa41968d5eb6a75938e6dc53183
hwcomposer: Use RGB_BORDERFILL only on MDP 4.2 and higher.

MDP 4.0 does not support RGB_BORDERFILL and causes the display to fail
initializing.

Patch Set 2: Actually set MDP_RGB format if not BORDERFILL.

Change-Id: Ib2007221c4dc78fd17ced97c0a0d28896c877b80
gralloc : Don't fallback to system heap for framebuffer allocations

MDP can not handle buffers from system heap, so try camera heap
first, before falling back completely to system heap

Change-Id: I7e2ab0094be5d1075be1ca93295cf54b84101835