msm: kgsl: Avoid a deadlock with the cmdbatch timer

Don't take the cmdbatch lock while deleting the cmdbatch timer.
This avoids a deadlock where del_timer_sync() waits for the timer
function which needs to take the lock.

CRs-Fixed: 644944
Change-Id: Iaeb5a26b67e96e8e748fb9ff8c26fa8b0f2c3827
Signed-off-by: Lynus Vaz <lvaz@codeaurora.org>