drm/i915/display: add I915 conditional build to intel_crt.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/89a6daca98f87ed1a8a54367a977f146216330d2.1694514689.git.jani.nikula@intel.com

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

@@ -12,9 +12,23 @@ enum pipe;
 struct drm_encoder;
 struct drm_i915_private;
 
+#ifdef I915
 bool intel_crt_port_enabled(struct drm_i915_private *dev_priv,
 			    i915_reg_t adpa_reg, enum pipe *pipe);
 void intel_crt_init(struct drm_i915_private *dev_priv);
 void intel_crt_reset(struct drm_encoder *encoder);
+#else
+static inline bool intel_crt_port_enabled(struct drm_i915_private *dev_priv,
+					  i915_reg_t adpa_reg, enum pipe *pipe)
+{
+	return false;
+}
+static inline void intel_crt_init(struct drm_i915_private *dev_priv)
+{
+}
+static inline void intel_crt_reset(struct drm_encoder *encoder)
+{
+}
+#endif
 
 #endif /* __INTEL_CRT_H__ */