vfb: use fb_sys_read() and fb_sys_write()

Since vfb's framebuffer is vmalloc'ed, use the fb_sys_read() and
fb_sys_write().
Signed-off-by: NAntonino Daplas <adaplas@gmail.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/video/Kconfig

@@ -1743,6 +1743,7 @@ config FB_VIRTUAL
 	select FB_SYS_FILLRECT
 	select FB_SYS_COPYAREA
 	select FB_SYS_IMAGEBLIT
+	select FB_SYS_FOPS
 	---help---
 	  This is a `virtual' frame buffer device. It operates on a chunk of
 	  unswappable kernel memory instead of on the memory of a graphics

drivers/video/vfb.c

@@ -84,6 +84,8 @@ static int vfb_mmap(struct fb_info *info,
 		    struct vm_area_struct *vma);
 
 static struct fb_ops vfb_ops = {
+	.fb_read        = fb_sys_read,
+	.fb_write       = fb_sys_write,
 	.fb_check_var	= vfb_check_var,
 	.fb_set_par	= vfb_set_par,
 	.fb_setcolreg	= vfb_setcolreg,