vbe: Support VBE simple

Add support for VBE simple, which permits firmware update of a single
image stored in MMC or another block device.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/boot/Kconfig b/boot/Kconfig
index e0f09e2..6b3b8f0 100644
--- a/boot/Kconfig
+++ b/boot/Kconfig
@@ -408,6 +408,18 @@
 	  supports selection of various firmware components, seleciton of an OS to
 	  boot as well as updating these using fwupd.
 
+if BOOTMETH_VBE
+
+config BOOTMETH_VBE_SIMPLE
+	bool "Bootdev support for VBE 'simple' method"
+	default y
+	help
+	  Enables support for VBE 'simple' boot. This allows updating a single
+	  firmware image in boot media such as MMC. It does not support any sort
+	  of rollback, recovery or A/B boot.
+
+endif # BOOTMETH_VBE
+
 config BOOTMETH_SANDBOX
 	def_bool y
 	depends on SANDBOX