drm/radeon: move ring debugfs into radeon_ring.c

Those debugfs files aren't r600 specific, so they
shouldn't be in r600.c. Move them to radeon_ring.c
and also add functionality to dump CP1 & CP2 ring
informations.

Signed-off-by: Christian König <deathsimple@vodafone.de>
Reviewed-by: Jerome Glisse <jglisse@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>