squashfs: fix memory leak in squashfs_fill_super

squashfs: fix memory leak in squashfs_fill_super

If sb_min_blocksize returns 0, squashfs_fill_super exits without freeing
allocated memory (sb->s_fs_info).

Fix this by moving the call to sb_min_blocksize to before memory is
allocated.

Link: https://lkml.kernel.org/r/20250811223740.110392-1-phillip@squashfs.org.uk
Fixes: 734aa85390ea ("Squashfs: check return result of sb_min_blocksize")
Signed-off-by: Phillip Lougher <phillip@squashfs.org.uk>
Reported-by: Scott GUO <scottzhguo@tencent.com>
Closes: https://lore.kernel.org/all/20250811061921.3807353-1-scott_gzh@163.com
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>