drm/i915: Rename conn_to_dig_port() to intel_attached_dig_port()

drm/i915: Rename conn_to_dig_port() to intel_attached_dig_port()

Use the standard naming convention and rename conn_to_dig_port()
to intel_attached_dig_port().

@@
@@
- conn_to_dig_port
+ intel_attached_dig_port
	(...)
{
...
}

@@
expression C;
@@
- conn_to_dig_port(C)
+ intel_attached_dig_port(C)

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191204180549.1267-9-ville.syrjala@linux.intel.com
Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>