fastboot: add UUU command UCmd and ACmd support

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>
diff --git a/drivers/fastboot/Kconfig b/drivers/fastboot/Kconfig
index a17e488..2d1836a 100644
--- a/drivers/fastboot/Kconfig
+++ b/drivers/fastboot/Kconfig
@@ -72,6 +72,15 @@
 	  the downloaded image to a non-volatile storage device. Define
 	  this to enable the "fastboot flash" command.
 
+config FASTBOOT_UUU_SUPPORT
+	bool "Enable FASTBOOT i.MX UUU special command"
+	default n
+	help
+	  The fastboot protocol includes "UCmd" and "ACmd" command.
+	  Be aware that you provide full access to any U-Boot command,
+	  including working with memory and may open a huge backdoor,
+	  when enabling this option.
+
 choice
 	prompt "Flash provider for FASTBOOT"
 	depends on FASTBOOT_FLASH