drm/msm/gem: Convert to lockdep assert

Utilize the power of lockdep for our GEM locking related sanity
checking.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Patchwork: https://patchwork.freedesktop.org/patch/496139/
Link: https://lore.kernel.org/r/20220802155152.1727594-16-robdclark@gmail.com