drm/i915/combo-phy: convert intel_combo_phy.[ch] to struct intel_display

drm/i915/combo-phy: convert intel_combo_phy.[ch] to struct intel_display

Going forward, struct intel_display is the main display device data
pointer. Convert as much as possible of intel_combo_phy.[ch] to struct
intel_display, along with intel_phy_is_combo() in intel_display.c.

Drive-by convert some drm_dbg() to drm_dbg_kms() while at it.

Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/c2e0a6294a8eaa4c16632881edc4f2d23c576101.1739378096.git.jani.nikula@intel.com