binman: doc: Add documentation to htmldocs

Add a link to binman's documentation and adjust the files so that it is
accessible. Use the name README.rst so it is easy to discover when binman
is installed without U-Boot.

Signed-off-by: Simon Glass <sjg@chromium.org>

tools/binman/control.py

@@ -569,7 +569,7 @@ def Binman(args):
         if not pager:
             pager = 'more'
         fname = os.path.join(os.path.dirname(os.path.realpath(sys.argv[0])),
-                            'README')
+                            'README.rst')
         command.Run(pager, fname)
         return 0