drm/i915/cnl: Add right GMBUS pin number for HDMI on Port F.

On CNP Pin 3 is for misc of Port F usage depending on the
configuration. For CNL that uses Port F, pin 3 is the one.

v2: Make it more generic and update commit message.

Cc: Anusha Srivatsa <anusha.srivatsa@intel.com>
Cc: Lucas De Marchi <lucas.demarchi@intel.com>
Cc: Manasi Navare <manasi.d.navare@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Reviewed-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180129232223.766-6-rodrigo.vivi@intel.com

drivers/gpu/drm/i915/intel_hdmi.c

@@ -1935,6 +1935,9 @@ static u8 cnp_port_to_ddc_pin(struct drm_i915_private *dev_priv,
 	case PORT_D:
 		ddc_pin = GMBUS_PIN_4_CNP;
 		break;
+	case PORT_F:
+		ddc_pin = GMBUS_PIN_3_BXT;
+		break;
 	default:
 		MISSING_CASE(port);
 		ddc_pin = GMBUS_PIN_1_BXT;