msm: mdss: compat ioctl for mdss overlay

Implement an entry point for compat ioctl in mdss overlay driver.
Overlay ioctls that require compat layer translation have been added here.
If the calling user process comes from a 32-bit world, then the compat
ioctl does an appropriate command conversion to keep the existing ioctl
implementation unchanged.  Add PP compat structures to include 32 bit
compatible versions of post-processing structures. This allows addition
of pp compat ioctl layer.

Change-Id: I732fcbc84151b813a02d3b4db20e858d4c51291e
Signed-off-by: Manoj Rao <manojraj@codeaurora.org>
Signed-off-by: Benet Clark <benetc@codeaurora.org>