drm/nouveau: dispnv50: fix missing-prototypes warning

nv50_display_create() is declared in another header, along with
a couple of declarations that are now outdated:

drivers/gpu/drm/nouveau/dispnv50/disp.c:2517:1: error: no previous prototype for 'nv50_display_create'

Fixes: ba801ef068 ("drm/nouveau/kms: display destroy/init/fini hooks can be static")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Karol Herbst <kherbst@redhat.com>
Signed-off-by: Karol Herbst <kherbst@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230417210329.2469722-1-arnd@kernel.org

drivers/gpu/drm/nouveau/dispnv50/disp.c

@@ -64,6 +64,7 @@
 #include "nouveau_connector.h"
 #include "nouveau_encoder.h"
 #include "nouveau_fence.h"
+#include "nv50_display.h"
 
 #include <subdev/bios/dp.h>
 

drivers/gpu/drm/nouveau/nv50_display.h

@@ -31,7 +31,5 @@
 #include "nouveau_reg.h"
 
 int  nv50_display_create(struct drm_device *);
-void nv50_display_destroy(struct drm_device *);
-int  nv50_display_init(struct drm_device *);
-void nv50_display_fini(struct drm_device *);
+
 #endif /* __NV50_DISPLAY_H__ */