radeon: straighten out the API insanity.

as Michel pointed out we are exposing too much info for these object
for this to be maintainable going forward.

This patch set minimises the exposed parts of the radeon_bo and
radeon_cs objects to the piece necessary for ddx/mesa to operate
at a decent speed.

The major problem is mesa contains a legacy BO/CS managers which we still
need to expose functionality to, and we really cannot change the API
until we can drop the non-KMS codepaths.

Signed-off-by: Dave Airlie <airlied@redhat.com>