ARM: mvebu: Add support for USB storage class in mvebu_defconfig

Some boards can have built-in USB storage class controllers so
it's better to have this option included by default.

Currently this option is needed to support built-in USB MMC controller
found in Globalscale Mirabox board.
Signed-off-by: NEzequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: NJason Cooper <jason@lakedaemon.net>

arch/arm/configs/mvebu_defconfig

@@ -60,6 +60,7 @@ CONFIG_USB_SUPPORT=y
 CONFIG_USB=y
 CONFIG_USB_EHCI_HCD=y
 CONFIG_USB_EHCI_ROOT_HUB_TT=y
+CONFIG_USB_STORAGE=y
 CONFIG_MMC=y
 CONFIG_MMC_MVSDIO=y
 CONFIG_NEW_LEDS=y