fs/ext4: Initialize group descriptor size for revision level 0 filesystems

genext2fs creates revision level 0 filesystems, which are not readable
by u-boot due to the initialized group descriptor size field.
f798b1dda1

Reported-by: Kever Yang <kever.yang@rock-chips.com>
Reported-by: FrostyBytes@protonmail.com
Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>
Tested-by: Kever Yang <kever.yang@rock-chips.com>

fs/ext4/ext4_common.c

@@ -2334,6 +2334,7 @@ int ext4fs_mount(unsigned part_length)
 
 	if (le32_to_cpu(data->sblock.revision_level) == 0) {
 		fs->inodesz = 128;
+		fs->gdsize = 32;
 	} else {
 		debug("EXT4 features COMPAT: %08x INCOMPAT: %08x RO_COMPAT: %08x\n",
 		      __le32_to_cpu(data->sblock.feature_compatibility),