uboot-imx

spl: drivers: Link usb common library to SPL if USB gadget is enabled

Some drivers might need to access common USB functions such as
usb_get_maximum_speed() or usb_get_dr_mode().

Signed-off-by: Jean-Jacques Hiblot <jjhiblot@ti.com>
Reviewed-by: Tom Rini <trini@konsulko.com>