upl: Add a command

Add a 'upl' command to work with Universal Payload features. For now it
only supports reading and writing a handoff structure.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/cmd/Makefile b/cmd/Makefile
index 87133cc..91227f1 100644
--- a/cmd/Makefile
+++ b/cmd/Makefile
@@ -189,6 +189,7 @@
 obj-$(CONFIG_CMD_UNIVERSE) += universe.o
 obj-$(CONFIG_CMD_UNLZ4) += unlz4.o
 obj-$(CONFIG_CMD_UNZIP) += unzip.o
+obj-$(CONFIG_CMD_UPL) += upl.o
 obj-$(CONFIG_CMD_VIRTIO) += virtio.o
 obj-$(CONFIG_CMD_WDT) += wdt.o
 obj-$(CONFIG_CMD_LZMADEC) += lzmadec.o