ext4: fix a copy and paste typo

This was obviously supposed to be an ext4 struct, not xfs.  GCC
doesn't care either way so it doesn't affect the build or runtime.

Fixes: cebe85d ("ext4: switch to the new mount api")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Lukas Czerner <lczerner@redhat.com>
Link: https://lore.kernel.org/r/20211215114309.GB14552@kili
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: Dan Carpenter

fs/ext4/super.c

@@ -2081,7 +2081,7 @@ static void ext4_fc_free(struct fs_context *fc)
 
 int ext4_init_fs_context(struct fs_context *fc)
 {
-	struct xfs_fs_context	*ctx;
+	struct ext4_fs_context *ctx;
 
 	ctx = kzalloc(sizeof(struct ext4_fs_context), GFP_KERNEL);
 	if (!ctx)