fs/fat: remove unnecessary defintion

'*sb' never used, so let's remote it and pass inode->i_sb directly to the
MSDOS_SB.

Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/fat/inode.c

@@ -1279,8 +1279,7 @@ out:
 
 static int fat_read_root(struct inode *inode)
 {
-	struct super_block *sb = inode->i_sb;
-	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
 	int error;
 
 	MSDOS_I(inode)->i_pos = MSDOS_ROOT_INO;