phy: Add support for phy-da8xx-usb

In preparation for supporting the musb driver, this patch
adds support for the usb phy associated with the musb driver.

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/drivers/phy/Makefile b/drivers/phy/Makefile
index 90646ca..b9f5195 100644
--- a/drivers/phy/Makefile
+++ b/drivers/phy/Makefile
@@ -21,3 +21,4 @@
 obj-$(CONFIG_OMAP_USB2_PHY) += omap-usb2-phy.o
 obj-$(CONFIG_KEYSTONE_USB_PHY) += keystone-usb-phy.o
 obj-$(CONFIG_MT76X8_USB_PHY) += mt76x8-usb-phy.o
+obj-$(CONFIG_PHY_DA8XX_USB) += phy-da8xx-usb.o