kernel: fix kmod-usb-phy-omap-usb2

upstream change in Kernel 3.18
commit: "phy: rename struct omap_control_usb to struct omap_control_phy"

Signed-off-by: Dirk Neukirchen <dirkneukirchen@web.de>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@45234 3c298f89-4303-0410-b956-a3cf2f4a3e73