drm/msm/gpu: Check the status of registration to PM QoS

There is a need to check the returned value of the registration function.
In case of returned error, print that and stop the init process.

Fixes: 7c0ffcd4 ("drm/msm/gpu: Respect PM QoS constraints")
Signed-off-by: Lukasz Luba <lukasz.luba@arm.com>
Patchwork: https://patchwork.freedesktop.org/patch/620336/


Signed-off-by: Rob Clark <robdclark@chromium.org>