drm/radeon/kms: add r1xx/r2xx support for CS_KEEP_TILING_FLAGS

Previous patch only updates r3xx+.  It's not likely
anyone will use this on r1xx/r2xx, but add it for consistency.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>