msm: mdss: Memset commit structure in compat path

Memset commit structure in compat path ioctl as some
of the pointer variables might go uninitialized, if not
explicitly initialized by userspace. These uninitialized
variables contain garbage values which can further result
in kernel crash.

Change-Id: I09518a43438e27751f2b918d682f551550c4342e
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>