Convert CONFIG_OMAP_USB_PHY to Kconfig

This converts the following to Kconfig:
   CONFIG_OMAP_USB_PHY

Signed-off-by: Adam Ford <aford173@gmail.com>
diff --git a/configs/cm_t43_defconfig b/configs/cm_t43_defconfig
index a621ff2..e234bc6 100644
--- a/configs/cm_t43_defconfig
+++ b/configs/cm_t43_defconfig
@@ -72,6 +72,7 @@
 CONFIG_USB=y
 CONFIG_USB_XHCI_HCD=y
 CONFIG_USB_XHCI_DWC3=y
+CONFIG_OMAP_USB_PHY=y
 CONFIG_USB_STORAGE=y
 CONFIG_FAT_WRITE=y
 CONFIG_OF_LIBFDT=y