usb: host/sl811-hcd: fix sparse warning

this patch fixes following sparse warning:
sl811-hcd.c:1804:24: warning: symbol 'sl811h_driver' was not declared. Should it be static?
Signed-off-by: NLad, Prabhakar <prabhakar.csengg@gmail.com>
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/sl811-hcd.c

@@ -1801,7 +1801,7 @@ sl811h_resume(struct platform_device *dev)
 
 
 /* this driver is exported so sl811_cs can depend on it */
-struct platform_driver sl811h_driver = {
+static struct platform_driver sl811h_driver = {
 	.probe =	sl811h_probe,
 	.remove =	sl811h_remove,