binman: Add support for passing arguments to entries

Sometimes it is useful to pass binman the value of an entry property from
the command line. For example some entries need access to files and it is
not always convenient to put these filenames in the image definition
(device tree).

Add a -a option which can be used like this:

   -a<prop>=<value>

where

   <prop> is the property to set
   <value> is the value to set it to

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/dtoc/fdt_util.py b/tools/dtoc/fdt_util.py
index 05cb9c0..b229038 100644
--- a/tools/dtoc/fdt_util.py
+++ b/tools/dtoc/fdt_util.py
@@ -147,3 +147,24 @@
     if propname in node.props:
         return True
     return default
+
+def GetDatatype(node, propname, datatype):
+    """Get a value of a given type from a property
+
+    Args:
+        node: Node object to read from
+        propname: property name to read
+        datatype: Type to read (str or int)
+
+    Returns:
+        value read, or None if none
+
+    Raises:
+        ValueError if datatype is not str or int
+    """
+    if datatype == str:
+        return GetString(node, propname)
+    elif datatype == int:
+        return GetInt(node, propname)
+    raise ValueError("fdt_util internal error: Unknown data type '%s'" %
+                     datatype)