test/py: Quote consistency

When converting test/py from " to ', I missed a few places (or added a
few inconsistencies later). Fix these.

Note that only quotes in code are converted; double-quotes in comments
and HTML are left as-is, since English and HTML use " not '.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Simon Glass <sjg@chromium.org>

test/py/tests/test_dfu.py

@@ -258,7 +258,7 @@ def test_dfu(u_boot_console, env__usb_dev_port, env__dfu_config):
         dfu_write(0, dummy_f.abs_fn)
 
         for size in sizes:
-            with u_boot_console.log.section("Data size %d" % size):
+            with u_boot_console.log.section('Data size %d' % size):
                 dfu_write_read_check(size)
                 # Make the status of each sub-test obvious. If the test didn't
                 # pass, an exception was thrown so this code isn't executed.