drm/msm/adreno: Call pm_runtime_force_suspend() during unbind

The GPU specific pm_suspend code assumes that the hardware is active
when the function is called, which it usually is when called as part
of pm_runtime.  But during unbind, the pm_suspend functions are called
blindly resulting in a bit of a when the hardware wasn't already
active (or booted, in the case of the GMU).

Instead of calling the pm_suspend function directly, use
pm_runtime_force_suspend() which should check the correct state of
runtime and call the functions on our behalf or skip them if they are
not needed.

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