msm: mdss: Add cursor validation for hflip

Hflip is not supported on cursor pipes as there
is no flip buffer in the hardware. Invalidate
any commit request for cursor hflip.

Change-Id: I4b0ad28caffb75a4bd5a928a90daa6aa59f51848
Signed-off-by: Animesh Kishore <animeshk@codeaurora.org>