arch/powerpc: 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.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: Michael Ellerman <mpe@ellerman.id.au>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Helge Deller <deller@gmx.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230417125651.25126-16-tzimmermann@suse.de

arch/powerpc/include/asm/fb.h

@@ -2,8 +2,8 @@
 #ifndef _ASM_FB_H_
 #define _ASM_FB_H_
 
-#include <linux/fb.h>
 #include <linux/fs.h>
+
 #include <asm/page.h>
 
 static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma,
@@ -13,10 +13,8 @@ static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma,
 						 vma->vm_end - vma->vm_start,
 						 vma->vm_page_prot);
 }
+#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_ */