test: Convert test_ut_dm_init() to use FsHelper

Use the helper here, for consistency.

Series-to: concept, heinrich
Cover-letter:
test: Create a better helper for filesystems
This series includes a few new helpers which make it easier to create
filesystems and disk images for testing.

The current approach requires the caller to create a temporary
directory, put files in there, then call the helper. It has poor support
for building disks containing multiple partitions.

This new helper works by creating a temporary directory which the caller
can use, then creating the filesystem and cleaning up.

Most of U-Boot is moved over to use these new helpers, but two EFI tests
are left alone, since they don't currently pass:

   - test_efi_eficonfig() has a 'return' in it, so doesn't run
   - TestEfiCapsuleFirmwareFit is skipped due to a failure at the start

These can be moved over later when they are working.

This series also includes a few quirks to the VBE tests.
END

Signed-off-by: Simon Glass <sjg@chromium.org>

test/py/tests/test_ut.py

@@ -580,8 +580,8 @@ def test_ut_dm_init(ubman):
         utils.run_and_log(
             ubman, f'sfdisk {fn}', stdin=b'type=83')
 
-    fs_helper.mk_fs(ubman.config, 'ext2', 0x200000, '2MB', None)
-    fs_helper.mk_fs(ubman.config, 'fat32', 0x100000, '1MB', None)
+    FsHelper(ubman.config, 'ext2', 2, '2MB').mk_fs()
+    FsHelper(ubman.config, 'fat32', 1, '1MB').mk_fs()
 
     mmc_dev = 6
     fn = os.path.join(ubman.config.source_dir, f'mmc{mmc_dev}.img')