fbdev: Move declaration of fb_class to <linux/fb.h>

Move the forward declaration of fb_class from drivers/video/console/fbcon.h to
<linux/fb.h>, together with the other forward declarations related to
drivers/video/fbmem.c.

This kills the following sparse warning:
| drivers/video/fbmem.c:1363:14: warning: symbol 'fb_class' was not declared. Should it be static?
Signed-off-by: Geert Uytterhoeven <Geert.Uytterhoeven@sonycom.com>
Signed-off-by: Antonino Daplas <adaplas@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/video/console/fbcon.h

@@ -176,7 +176,6 @@ extern void fbcon_set_tileops(struct vc_data *vc, struct fb_info *info);
 #endif
 extern void fbcon_set_bitops(struct fbcon_ops *ops);
 extern int  soft_cursor(struct fb_info *info, struct fb_cursor *cursor);
-extern struct class *fb_class;
 
 #define FBCON_ATTRIBUTE_UNDERLINE 1
 #define FBCON_ATTRIBUTE_REVERSE   2

include/linux/fb.h

@@ -942,6 +942,7 @@ extern int fb_new_modelist(struct fb_info *info);
 
 extern struct fb_info *registered_fb[FB_MAX];
 extern int num_registered_fb;
+extern struct class *fb_class;
 
 static inline void __fb_pad_aligned_buffer(u8 *dst, u32 d_pitch,
 					   u8 *src, u32 s_pitch, u32 height)