drm/doc: Document submission error signaling

Different approaches have been tried to signal resets and other errors in
vendor specific ways which not only resulted in a wide variety of
implementations but also repeating the same bugs and problems over different
drivers.

Document that drivers should use dma_fence based error signaling which is
vendor agnostic and allows userspace to query submission errors in generic
non-vendor specific code.

Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240826122541.85663-3-christian.koenig@amd.com