drm: msm: adreno: Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) +PTR_ERR

Use PTR_ERR_OR_ZERO rather than if(IS_ERR(...)) + PTR_ERR because its
better to have inlined function rather than code-opened implementation.

Signed-off-by: Mamta Shukla <mamtashukla555@gmail.com>
Reviewed-by: Sean Paul <sean@poorly.run>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20181018204815.GA23390@armorer