fs/ufs/super.c: remove set but not used variable 'usb3'

Fixes gcc '-Wunused-but-set-variable' warning:

  fs/ufs/super.c: In function ufs_statfs:
  fs/ufs/super.c:1409:32: warning: variable usb3 set but not used [-Wunused-but-set-variable]

It is not used since commmit c596961d ("ufs: fix s_size/s_dsize
users")

Link: http://lkml.kernel.org/r/20190525140654.15924-1-yuehaibing@huawei.comSigned-off-by: YueHaibing <yuehaibing@huawei.com>
Cc: Evgeniy Dushistov <dushistov@mail.ru>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/ufs/super.c

@@ -1407,11 +1407,9 @@ static int ufs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	struct super_block *sb = dentry->d_sb;
 	struct ufs_sb_private_info *uspi= UFS_SB(sb)->s_uspi;
 	unsigned  flags = UFS_SB(sb)->s_flags;
-	struct ufs_super_block_third *usb3;
 	u64 id = huge_encode_dev(sb->s_bdev->bd_dev);
 
 	mutex_lock(&UFS_SB(sb)->s_lock);
-	usb3 = ubh_get_usb_third(uspi);
 	
 	if ((flags & UFS_TYPE_MASK) == UFS_TYPE_UFS2)
 		buf->f_type = UFS2_MAGIC;