msm: mdss: Make mdp sync point generic to use

Currently mdp sync point supports buf sync ioctl for
normal mdp overlay operation. So making it more generic
such that it can be used for rotator also.

Change-Id: I04c5f29a5259238ef1de26f6e801269b89cf5fed
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>