arch/m68k: Implement <asm/fb.h> with generic helpers

Replace the architecture's fb_is_primary_device() with the generic
one from <asm-generic/fb.h>. No functional changes.

v2:
	* provide empty fb_pgprotect() on non-MMU systems
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Helge Deller <deller@gmx.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230417125651.25126-9-tzimmermann@suse.de

arch/m68k/include/asm/fb.h

@@ -2,11 +2,11 @@
 #ifndef _ASM_FB_H_
 #define _ASM_FB_H_
 
-#include <linux/fb.h>
-#include <linux/fs.h>
 #include <asm/page.h>
 #include <asm/setup.h>
 
+struct file;
+
 static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma,
 				unsigned long off)
 {
@@ -24,10 +24,8 @@ static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma,
 #endif /* CONFIG_SUN3 */
 #endif /* CONFIG_MMU */
 }
+#define fb_pgprotect fb_pgprotect
 
-static inline int fb_is_primary_device(struct fb_info *info)
-{
-	return 0;
-}
+#include <asm-generic/fb.h>
 
 #endif /* _ASM_FB_H_ */