drm/sysfs: split DVI-I and TV-out attributes

The show methods for the attributes of DVI-I and TV-out types have a
bunch of code to deal with the differences between the two. Just split
the attributes into connector type specific ones. No functional changes.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>