drm: remove pointless checks in radeon_state

If these were valid checks, we'd have already oopsed several
lines above where we were already dereferencing them.

DA: these used to be valid but other changes made them unnecessary.

Coverity: 776,777,778
Signed-off-by: Dave Jones <davej@redhat.com>
Signed-off-by: Dave Airlie <airlied@linux.ie>