msm: mdss: modify userspace src format during MSMFB_SET on rotator

The req->src.format field should be changed to the destination
format and propagated to the user so that appropriate buffer size
calculations for the destination buffer can be made. Note, this
only changes the user copy and the driver fetches the source buffer
based on source format.

CRs-fixed: 686496
Change-Id: I590829796c00aeea8e3d9b10578126dd7afe9c82
Signed-off-by: Sree Sesha Aravind Vadrevu <svadrevu@codeaurora.org>