configs: powerpc: add usb (host) mass storage support

commit 0cfccb54 ("configs: Resync with savedefconfig")
removed CONFIG_USB_STORAGE from some powerpc platforms' defconfig
files, whicih would block the use case of system loading rootfs
from USB drives, add them back.

Signed-off-by: Ran Wang <ran.wang_1@nxp.com>
Reviewed-by: Tom Rini <trini@konsulko.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>