msm: mdss: Swap RGBA format to BGRA with bwc rotation

When BWC is enabled, rotator format needs to be swapped from
RGBA to BGRA to avoid color mismatch on the ouput image.
This is specially needed with a GPU composed FB.

Change-Id: I956a354f3fe605e2c7bda4c4331cfe5bcd6417c7
Signed-off-by: Sree Sesha Aravind Vadrevu <svadrevu@codeaurora.org>