USB: ehci-spear: Make of_device_id array const

Make of_device_id array const, because all OF functions handle
it as const.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
diff --git a/drivers/usb/host/ehci-spear.c b/drivers/usb/host/ehci-spear.c
index 1d59958..1355ff0 100644
--- a/drivers/usb/host/ehci-spear.c
+++ b/drivers/usb/host/ehci-spear.c
@@ -150,7 +150,7 @@
 	return 0;
 }
 
-static struct of_device_id spear_ehci_id_table[] = {
+static const struct of_device_id spear_ehci_id_table[] = {
 	{ .compatible = "st,spear600-ehci", },
 	{ },
 };