add support for the UUU commands ACmd and UCmd.

Enable them through the Kconfig option
CONFIG_FASTBOOT_UUU_SUPPORT

base was commit in NXP kernel
9b149c2a2882: ("MLK-18591-3 android: Add FSL android fastboot support")

and ported it to current mainline. Tested this patch
on imx6ul based board.

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Patrick Delaunay <patrick.delaunay@foss.st.com>