msm: kgsl: Only snapshot GMU on GMU boot failure

GMU boot failure is a special case so treat it as one.
Since most of adreno is not yet up and running there is no
point in trying to snapshot it all.
Dump as much GMU information as is possible and then return.

Change-Id: I8ad9b8406a7518d2c7fe76292843b4cda8e89ecd
Signed-off-by: Carter Cooper <ccooper@codeaurora.org>