fbdev/core: Move logo functions into separate source file

Move the fbdev function for displaying boot-up logos into their
own file fb_logo.c. Only build fb_logo.c if CONFIG_LOGO has been
selected. No functional changes.

v2:
	* include fb_internal.h (kernel test robot)
	* simplify option-parsing ifdefs
	* build fb_logo.o iff CONFIG_LOGO has been set

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Acked-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230907085408.9354-6-tzimmermann@suse.de

drivers/video/fbdev/core/Makefile

@@ -23,6 +23,8 @@ fb-y				  += fbcon_rotate.o fbcon_cw.o fbcon_ud.o \
 endif
 endif
 
+fb-$(CONFIG_LOGO)		  += fb_logo.o
+
 obj-$(CONFIG_FB_CFB_FILLRECT)  += cfbfillrect.o
 obj-$(CONFIG_FB_CFB_COPYAREA)  += cfbcopyarea.o
 obj-$(CONFIG_FB_CFB_IMAGEBLIT) += cfbimgblt.o

drivers/video/fbdev/core/fb_internal.h

@@ -20,7 +20,7 @@ static inline void fb_unregister_chrdev(void)
 { }
 #endif
 
-/* fbmem.c */
+/* fb_logo.c */
 #if defined(CONFIG_LOGO)
 extern bool fb_center_logo;
 extern int fb_logo_count;
@@ -37,6 +37,7 @@ static inline int fb_show_logo(struct fb_info *info, int rotate)
 }
 #endif /* CONFIG_LOGO */
 
+/* fbmem.c */
 extern struct class *fb_class;
 extern struct mutex registration_lock;
 extern struct fb_info *registered_fb[FB_MAX];