msm: kgsl: Add exceptions to snapshot based on GX and SPTP status

It is possible that during a GPU/GMU hang either the entire GX
is powered off or just the SPTPRAC headswitch is turned off
by the GMU firmware. Therefore, while doing snapshot check
if we have the blocks powered on before trying to dump them.

In addition, mask all GMU interrupts prior to dumping
snapshot in order to reduce instability.

CRs-Fixed: 2062271
Change-Id: I7bf7d27bc6ebdc642e5675a4c9645957051273d5
Signed-off-by: Shrenuj Bansal <shrenujb@codeaurora.org>
Signed-off-by: George Shen <sqiao@codeaurora.org>