panfrost: Add PAN_MESA_DEBUG=sync

panfrost: Add PAN_MESA_DEBUG=sync

Sometimes it's useful to get information about GPU faults in the
console, so it's synchronized with other messages.

This commit will cause Mesa to wait for completion and check if there
are any faults raised by the GPU.

Signed-off-by: Tomeu Vizoso <tomeu.vizoso@collabora.com>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>