usb: fix hcd h20ahb driver depends

USB_EHCI_HCD_SYNOPSYS is not only dependent on USB_EHCI_HCD, but
also on USB_PHY. Otherwise kernel build has the following error:

  LD      init/built-in.o
drivers/built-in.o: In function `ehci_hcd_h20ahb_probe':
:(.text+0xb9bb4): undefined reference to `usb_add_phy_dev'

Signed-off-by: Alex Shi <alex.shi@linaro.org>
1 file changed