Revert "drm/radeon: add missing hdmi callbacks for rv6xx"

This reverts commit b2a94840.

Commit 99d79aa2f3b7729e7290e8bda5d0dd8b0240ec62 (backported by
b2a94840) was supposed to fix rv6xx_asic
struct.

In kernel 3.10 we didn't have that struct yet, so the original patch
should never be backported to the 3.10. Accidentally it has applied and
modified different struct (r520_asic) that shouldn't have any HDMI
callbacks at all.

Signed-off-by: Rafał Miłecki <zajec5@gmail.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>