fbdev/via: fix defined but not used warning

Fix a build warning in viafbdev.c when CONFIG_PROC_FS is not enabled
by marking the unused function as __maybe_unused.

../drivers/video/fbdev/via/viafbdev.c:1471:12: warning: 'viafb_sup_odev_proc_show' defined but not used [-Wunused-function]
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Florian Tobias Schandinat <FlorianSchandinat@gmx.de>
Signed-off-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>

drivers/video/fbdev/via/viafbdev.c

@@ -19,6 +19,7 @@
  * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  */
 
+#include <linux/compiler.h>
 #include <linux/module.h>
 #include <linux/seq_file.h>
 #include <linux/slab.h>
@@ -1468,7 +1469,7 @@ static const struct file_operations viafb_vt1636_proc_fops = {
 
 #endif /* CONFIG_FB_VIA_DIRECT_PROCFS */
 
-static int viafb_sup_odev_proc_show(struct seq_file *m, void *v)
+static int __maybe_unused viafb_sup_odev_proc_show(struct seq_file *m, void *v)
 {
 	via_odev_to_seq(m, supported_odev_map[
 		viaparinfo->shared->chip_info.gfx_chip_name]);