msm: kgsl: Remove the "global" locking from the ioctl path

Remove the lock code from the generic ioctl handler and move the
mutex lock/unlock code to the places that really need it.  In
particular try not to hold a lock while doing user memory functions
(copy_to_user/copy_from_user) to avoid the potential of a deadlock
with the memory semaphore.

CRs-Fixed: 671080
Change-Id: Ic0dedbad6f7325b53d71a5dbbed50f92483871c8
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>