binman: Add support for u-boot.img as an input binary

Add an entry type for u-boot.img (a legacy U-Boot image) and a simple test.

Signed-off-by: Simon Glass <sjg@chromium.org>
Tested-by: Bin Meng <bmeng.cn@gmail.com>

tools/binman/func_test.py

@@ -713,3 +713,8 @@ class TestFunctional(unittest.TestCase):
             first = data[:len(U_BOOT_NODTB_DATA)]
             self.assertEqual('nodtb with microcode' + pos_and_size +
                             ' somewhere in here', first)
+
+    def testUBootImg(self):
+        """Test that u-boot.img can be put in a file"""
+        data = self._DoReadFile('36_u_boot_img.dts')
+        self.assertEqual(U_BOOT_IMG_DATA, data)