freedreno/drm: don't pass thru 'DUMP' flag on older kernels

freedreno/drm: don't pass thru 'DUMP' flag on older kernels

"softpin" mode was introduced in the same kernel as the 'DUMP' flag.  So
if we are using the legacy non-softpin path, clear the dump flag.  OTOH
the 'DUMP' flag isn't quite so needed on older kernels, since we would
get all cmdstream, even SDS stateobjs, dumped regardless, as they would
have cmd table entries.

Fixes: b2c23b1e48f ("freedreno: Mark all ringbuffer BOs as to be dumped on crash.")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Tested-by: Ilia Mirkin <imirkin@alum.mit.edu>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5081>