drm/msm/adreno: Load the firmware before bringing up the hardware

Failure to load firmware is the primary reason to fail adreno_load_gpu().
Try to load it first before going into the hardware initialization code and
unwinding it. This is important for a6xx because the GMU gets loaded from
the runtime power code and it is more costly to fail in that path because
of missing firmware.

Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>