drm/i915/display: add I915 conditional build to g4x_hdmi.h

Add stubs for !I915.
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Acked-by: Dave Airlie <airlied@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/ba2eea7ac081d0858a573062f197e00f3b186faf.1694514689.git.jani.nikula@intel.com

drivers/gpu/drm/i915/display/g4x_hdmi.h

@@ -15,9 +15,21 @@ struct drm_atomic_state;
 struct drm_connector;
 struct drm_i915_private;
 
+#ifdef I915
 void g4x_hdmi_init(struct drm_i915_private *dev_priv,
 		   i915_reg_t hdmi_reg, enum port port);
 int g4x_hdmi_connector_atomic_check(struct drm_connector *connector,
 				    struct drm_atomic_state *state);
+#else
+static inline void g4x_hdmi_init(struct drm_i915_private *dev_priv,
+				 i915_reg_t hdmi_reg, int port)
+{
+}
+static inline int g4x_hdmi_connector_atomic_check(struct drm_connector *connector,
+						  struct drm_atomic_state *state)
+{
+	return 0;
+}
+#endif
 
 #endif