msm: kgsl: Avoid sending 0 BW and GPU freq to GMU

Resetting GPU frequency or BW has to use PDC sleep
sequence. GMU cannot handle zero BW and GPU frequency
request. Dump GMU snapshot to help debug GMU DCVS failure.

CRs-Fixed: 2062271
Change-Id: Ibf6f4cfdfc406b4990b34cc7469c722bfc0f4879
Signed-off-by: George Shen <sqiao@codeaurora.org>