usb: build drivers/usb/common/ when USB_SUPPORT is set

PHY drivers can use ULPI interfaces when CONFIG_USB (which is host side
support) is not enabled, so also build drivers/usb/ when CONFIG_USB_SUPPORT
is enabled so that drivers/usb/common/ is built.

ERROR: "ulpi_unregister_driver" [drivers/phy/ti/phy-tusb1210.ko] undefined!
ERROR: "__ulpi_register_driver" [drivers/phy/ti/phy-tusb1210.ko] undefined!
ERROR: "ulpi_read" [drivers/phy/ti/phy-tusb1210.ko] undefined!
ERROR: "ulpi_write" [drivers/phy/ti/phy-tusb1210.ko] undefined!
ERROR: "ulpi_unregister_driver" [drivers/phy/qualcomm/phy-qcom-usb-hs.ko] undefined!
ERROR: "__ulpi_register_driver" [drivers/phy/qualcomm/phy-qcom-usb-hs.ko] undefined!
ERROR: "ulpi_write" [drivers/phy/qualcomm/phy-qcom-usb-hs.ko] undefined!

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>