drm/msm: Reject MAP_NULL op if no PRR

drm/msm: Reject MAP_NULL op if no PRR

We need PRR support in order to implement MAP_NULL.  Userspace shouldn't
be trying to use this if it is unsupported.

Reported-by: Valentine Burley <valentine.burley@collabora.com>
Link: https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/37935#note_3153730
Signed-off-by: Rob Clark <robin.clark@oss.qualcomm.com>
Tested-by: Valentine Burley <valentine.burley@collabora.com>
Patchwork: https://patchwork.freedesktop.org/patch/682941/
Message-ID: <20251022222051.10030-1-robin.clark@oss.qualcomm.com>