ext4: remove an unused statement in ext4_mb_get_buddy_page_lock()

In this patch, the statement "poff = block % blocks_per_page"
in ext4_mb_get_buddy_page_lock has no effect.

It will be optimized out by the compiler, but it's better to remove it.
Signed-off-by: NHaibo Liu <HaiboLiu6@gmail.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

fs/ext4/mballoc.c

@@ -969,7 +969,6 @@ static int ext4_mb_get_buddy_page_lock(struct super_block *sb,
 
 	block++;
 	pnum = block / blocks_per_page;
-	poff = block % blocks_per_page;
 	page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
 	if (!page)
 		return -EIO;