uapi: msm: mdss: expose compression ratio for rotator

For bandwidth calculations, rotator driver needs
to know the compression ratio factors which
depends on the pixel format. This change adds
support to share this information between
user-space and rotator driver.

Change-Id: I6163317514328610a836c34fd9ca75c3e753b50f
Signed-off-by: Ingrid Gallardo <ingridg@codeaurora.org>