drm/i915: Dump 'output_types' in crtc state dump

drm/i915: Dump 'output_types' in crtc state dump

To make it easier to debug things let's dump the output types bitmask in
the crtc state dump. And to make life that much better, let's pretty
print it as a a human reaadable string as well.

v2: Have the caller pass in the buffer (Chris)
    #undef OUTPUT_TYPE (Jani)

Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20171010121207.570-2-ville.syrjala@linux.intel.com
Reviewed-by: Jani Nikula <jani.nikula@intel.com>