drm/msm: Wait for MMU devcoredump when waiting for GMU

drm/msm: Wait for MMU devcoredump when waiting for GMU

If there is a flood of faults then the MMU can become saturated while it
waits for the kernel to process the first fault and resume it, so that
the GMU becomes blocked. This is mainly a problem when the kernel reads
the state of the GPU for a devcoredump, because this takes a while. If
we timeout waiting for the GMU, check if this has happened and retry
after we're finished.

Signed-off-by: Connor Abbott <cwabbott0@gmail.com>
Patchwork: https://patchwork.freedesktop.org/patch/664685/
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>