DRM/radeon: For single CRTC GPUs move handling of CRTC_CRT_ON to crtc_dpms().

On all dual CRTC GPUs the CRTC_CRT_ON in the RADEON_CRTC_EXT_CNTL register
 controls the CRTC of the primary DAC. Therefore it is set in the DAC DMPS
function.
This is different for GPU's with a single CRTC but a primary and a
TV DAC: here it controls the single CRTC no matter where it is routed.
Therefore we set it here. This avoids an elaborate on/off state tracking
since both primary_dac_dpms() and tv_dac_dpms() functions would have
to touch this bit.
On single CRTC GPUs with just one DAC it's irrelevant where this bit
is handled.

agd5f: fix warning

Signed-off-by: Egbert Eich <eich@suse.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>