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>
diff --git a/configs/cm_fx6_defconfig b/configs/cm_fx6_defconfig
index 7ad5c21..07a84bb 100644
--- a/configs/cm_fx6_defconfig
+++ b/configs/cm_fx6_defconfig
@@ -15,4 +15,8 @@
 CONFIG_SPI_FLASH=y
 CONFIG_CMD_SF=y
 CONFIG_CMD_I2C=y
+CONFIG_USB=y
 CONFIG_CMD_USB=y
+CONFIG_USB_EHCI_HCD=y
+CONFIG_USB_EHCI_MX6=y
+CONFIG_USB_STORAGE=y