drm/i915/hdmi: remove unused intel_hdmi_hdcp2_protocol()

Unused, hiding from the compiler warnings behind the inline keyword.
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/20200420140438.14672-1-jani.nikula@intel.com

drivers/gpu/drm/i915/display/intel_hdmi.c

@@ -1750,12 +1750,6 @@ int intel_hdmi_hdcp2_capable(struct intel_digital_port *intel_dig_port,
 	return ret;
 }
 
-static inline
-enum hdcp_wired_protocol intel_hdmi_hdcp2_protocol(void)
-{
-	return HDCP_PROTOCOL_HDMI;
-}
-
 static const struct intel_hdcp_shim intel_hdmi_hdcp_shim = {
 	.write_an_aksv = intel_hdmi_hdcp_write_an_aksv,
 	.read_bksv = intel_hdmi_hdcp_read_bksv,