usb: add static to local symbols

Sparse reports "... was not declared. Should it be static?"

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c
index 13aa70d..f08709d 100644
--- a/drivers/usb/host/ehci-hcd.c
+++ b/drivers/usb/host/ehci-hcd.c
@@ -937,7 +937,7 @@
 	return -1;
 }
 
-const struct ehci_ops default_ehci_ops = {
+static const struct ehci_ops default_ehci_ops = {
 	.set_usb_mode		= ehci_set_usbmode,
 	.get_port_speed		= ehci_get_port_speed,
 	.powerup_fixup		= ehci_powerup_fixup,