fbdev/xen-fbfront: Select FB_SYS_HELPERS_DEFERRED

The Kconfig token FB_SYS_HELPERS_DEFERRED selects everything that
is required for deferred I/O on system-memory framebuffers. Select
it from XEN_FBDEV_FRONTEND in favor of the existing identical selection.
Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Acked-by: Helge Deller <deller@gmx.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20230706151432.20674-10-tzimmermann@suse.de

drivers/video/fbdev/Kconfig

@@ -2065,11 +2065,7 @@ config FB_VIRTUAL
 config XEN_FBDEV_FRONTEND
 	tristate "Xen virtual frame buffer support"
 	depends on FB && XEN
-	select FB_SYS_FILLRECT
-	select FB_SYS_COPYAREA
-	select FB_SYS_IMAGEBLIT
-	select FB_SYS_FOPS
-	select FB_DEFERRED_IO
+	select FB_SYS_HELPERS_DEFERRED
 	select XEN_XENBUS_FRONTEND
 	default y
 	help