libcopybit: Add missing return statement

Change-Id: I662699b7418eba2c4792ed6c7c7b628762ebe03b
(cherry picked from commit f2e940109252c63b6e21f929e45ba794dfe12b95)
copybit: Fix type conversion error for GCC 4.7

    GCC 4.7 has stricter type conversion rules in copybit.cpp

Change-Id: I7f8572e2d9416ccb2ba17e707c7f75a2e69d69cf
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