drm/i915/icl: create function to identify combophy port

This patch creates a function/wrapper to check if port is combophy port
instead of explicitly comparing ports.

Changes since V1:
 - keep all intel_port_is_* helper together (Lucas)

Signed-off-by: Mahesh Kumar <mahesh1.kumar@intel.com>
Cc: Madhav Chauhan <madhav.chauhan@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181004085043.10154-1-mahesh1.kumar@intel.com
(cherry picked from commit 176597a12d)
Signed-off-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>

drivers/gpu/drm/i915/intel_display.c

@@ -5961,6 +5961,17 @@ static void i9xx_pfit_enable(struct intel_crtc *crtc)
 	I915_WRITE(BCLRPAT(crtc->pipe), 0);
 }
 
+bool intel_port_is_combophy(struct drm_i915_private *dev_priv, enum port port)
+{
+	if (port == PORT_NONE)
+		return false;
+
+	if (IS_ICELAKE(dev_priv))
+		return port <= PORT_B;
+
+	return false;
+}
+
 bool intel_port_is_tc(struct drm_i915_private *dev_priv, enum port port)
 {
 	if (IS_ICELAKE(dev_priv))