drm/armada: Hide fbdev support behind config option

Only build armada's fbdev emulation if CONFIG_DRM_FBDEV_EMULATION
has been enabled. No functional changes, but allows to build armada
without fbdev.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sui Jingfeng <suijingfeng@loongson.cn>
Link: https://patchwork.freedesktop.org/patch/msgid/20230330073046.7150-3-tzimmermann@suse.de

drivers/gpu/drm/armada/Makefile

 # SPDX-License-Identifier: GPL-2.0
-armada-y	:= armada_crtc.o armada_drv.o armada_fb.o armada_fbdev.o \
+armada-y	:= armada_crtc.o armada_drv.o armada_fb.o \
 		   armada_gem.o armada_overlay.o armada_plane.o armada_trace.o
 armada-y	+= armada_510.o
 armada-$(CONFIG_DEBUG_FS) += armada_debugfs.o
+armada-$(CONFIG_DRM_FBDEV_EMULATION) += armada_fbdev.o
 
 obj-$(CONFIG_DRM_ARMADA) := armada.o

drivers/gpu/drm/armada/armada_drm.h

@@ -75,8 +75,18 @@ struct armada_private {
 
 #define drm_to_armada_dev(dev) container_of(dev, struct armada_private, drm)
 
-int armada_fbdev_init(struct drm_device *);
-void armada_fbdev_fini(struct drm_device *);
+#if defined(CONFIG_DRM_FBDEV_EMULATION)
+int armada_fbdev_init(struct drm_device *dev);
+void armada_fbdev_fini(struct drm_device *dev);
+#else
+static inline int armada_fbdev_init(struct drm_device *dev)
+{
+	return 0;
+}
+
+static inline void armada_fbdev_fini(struct drm_device *dev)
+{ }
+#endif
 
 int armada_overlay_plane_create(struct drm_device *, unsigned long);