binman: Support alignment of files

When packing files it is sometimes useful to align the start of each file,
e.g. if the flash driver can only access 32-bit-aligned data. Provides a
new property to support this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/dtoc/fdt.py b/tools/dtoc/fdt.py
index 965106a..25ce513 100644
--- a/tools/dtoc/fdt.py
+++ b/tools/dtoc/fdt.py
@@ -463,6 +463,18 @@
         val = bytes(val, 'utf-8')
         self.AddData(prop_name, val + b'\0')
 
+    def AddInt(self, prop_name, val):
+        """Add a new integer property to a node
+
+        The device tree is marked dirty so that the value will be written to
+        the blob on the next sync.
+
+        Args:
+            prop_name: Name of property to add
+            val: Integer value of property
+        """
+        self.AddData(prop_name, struct.pack('>I', val))
+
     def AddSubnode(self, name):
         """Add a new subnode to the node
 
diff --git a/tools/dtoc/test_fdt.py b/tools/dtoc/test_fdt.py
index dc6943f..e8fbbd5 100755
--- a/tools/dtoc/test_fdt.py
+++ b/tools/dtoc/test_fdt.py
@@ -397,6 +397,12 @@
         data = self.fdt.getprop(self.node.Offset(), 'one')
         self.assertEqual(1, fdt32_to_cpu(data))
 
+        val = 1234
+        self.node.AddInt('integer', val)
+        self.dtb.Sync(auto_resize=True)
+        data = self.fdt.getprop(self.node.Offset(), 'integer')
+        self.assertEqual(val, fdt32_to_cpu(data))
+
         val = '123' + chr(0) + '456'
         self.node.AddString('string', val)
         self.dtb.Sync(auto_resize=True)