msm: kgsl: Don't delete uninitialized preemption timer

If we delete uninitialized timer on CONFIG_DEBUG_OBJECTS
disabled build del_timer_sync() will block for ever. For
all A3xx targets preemption timer is not initialized, but
dispatcher fault handler is trying to delete the
uninitialized preemption timer. Fix this issue by adding
a preemption check before we delete it.

CRs-Fixed: 2023690
Change-Id: I2c51a0b2286b82bf2eb5ee68d923dd9585f07f00
Signed-off-by: Wenbin Wang <wwenbin@codeaurora.org>
Signed-off-by: Abhilash Kumar <krabhi@codeaurora.org>