dtoc: Add support for building a dtoc PyPi package

Create the necessary files to build this new package.

This is needed for binman.

Move the main program into a function so that it can easily be called by
the PyPi-created script.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/Makefile b/Makefile
index f4ffa9e..bf6abe5 100644
--- a/Makefile
+++ b/Makefile
@@ -2284,6 +2284,7 @@
 	scripts/make_pip.sh u_boot_pylib ${PIP_ARGS}
 	scripts/make_pip.sh patman ${PIP_ARGS}
 	scripts/make_pip.sh buildman ${PIP_ARGS}
+	scripts/make_pip.sh dtoc ${PIP_ARGS}
 
 help:
 	@echo  'Cleaning targets:'