uboot-imx

arm: mx6: usb: kconfig: add USB_EHCI_MX6 kconfig option

Add USB_EHCI_MX6 option to menuconfig and use it when migrating cm-fx6 usb
config to defconfig.

Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Stefano Babic <sbabic@denx.de>
Cc: Igor Grinberg <grinberg@compulab.co.il>
Signed-off-by: Nikita Kiryanov <nikita@compulab.co.il>
Acked-by: Igor Grinberg <grinberg@compulab.co.il>