binman: Read map files as text

These files are text files so should be read as such, so that
string-equality assertions work as expected.

With this binman tests work correctly on Python 2 and Python 3:

PYTHONPATH=/tmp/b/sandbox_spl/scripts/dtc/pylibfdt \
	python ./tools/binman/binman -t

Change first line of binman.py to end "python3":

PYTHONPATH=~/cosarm/dtc/pylibfdt:tools/patman \
	python3 ./tools/binman/binman -t
Signed-off-by: NSimon Glass <sjg@chromium.org>

tools/binman/ftest.py

@@ -1777,7 +1777,7 @@ class TestFunctional(unittest.TestCase):
         # We should not get an inmage, but there should be a map file
         self.assertFalse(os.path.exists(tools.GetOutputFilename('image.bin')))
         self.assertTrue(os.path.exists(map_fname))
-        map_data = tools.ReadFile(map_fname)
+        map_data = tools.ReadFile(map_fname, binary=False)
         self.assertEqual('''ImagePos    Offset      Size  Name
 <none>    00000000  00000007  main-section
 <none>     00000000  00000004  u-boot