mfd: omap-usb-host: Make of_device_id array const

Array of struct of_device_id may be be const as expected by
of_platform_populate() call.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
diff --git a/drivers/mfd/omap-usb-host.c b/drivers/mfd/omap-usb-host.c
index 651e249..b48d80c 100644
--- a/drivers/mfd/omap-usb-host.c
+++ b/drivers/mfd/omap-usb-host.c
@@ -557,7 +557,7 @@
 	return 0;
 }
 
-static struct of_device_id usbhs_child_match_table[] = {
+static const struct of_device_id usbhs_child_match_table[] = {
 	{ .compatible = "ti,omap-ehci", },
 	{ .compatible = "ti,omap-ohci", },
 	{ }