fastboot: Add support for 'oem format' command

Introduce 'oem format' which matches the USB implementation, guard this
with CONFIG_FASTBOOT_CMD_OEM_FORMAT so that you can configure it out.

Signed-off-by: Alex Kiernan <alex.kiernan@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/fastboot/Kconfig b/drivers/fastboot/Kconfig
index 625f016..bc25ea1 100644
--- a/drivers/fastboot/Kconfig
+++ b/drivers/fastboot/Kconfig
@@ -124,6 +124,14 @@
 	  specified on the "fastboot flash" command line matches the value
 	  defined here. The default target name for updating MBR is "mbr".
 
+config FASTBOOT_CMD_OEM_FORMAT
+	bool "Enable the 'oem format' command"
+	depends on FASTBOOT_FLASH_MMC && CMD_GPT
+	help
+	  Add support for the "oem format" command from a client. This
+	  relies on the env variable partitions to contain the list of
+	  partitions as required by the gpt command.
+
 endif # FASTBOOT
 
 endmenu