fs: drop redundant check from __writeback_single_inode()

wbc->for_sync implies wbc->sync_mode == WB_SYNC_ALL, so there's no need
to check for both.  Just check for WB_SYNC_ALL.

Link: https://lore.kernel.org/r/20210112190253.64307-9-ebiggers@kernel.orgReviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Jan Kara <jack@suse.cz>

fs/fs-writeback.c

@@ -1479,7 +1479,7 @@ __writeback_single_inode(struct inode *inode, struct writeback_control *wbc)
 	 * change I_DIRTY_TIME into I_DIRTY_SYNC.
 	 */
 	if ((inode->i_state & I_DIRTY_TIME) &&
-	    (wbc->sync_mode == WB_SYNC_ALL || wbc->for_sync ||
+	    (wbc->sync_mode == WB_SYNC_ALL ||
 	     time_after(jiffies, inode->dirtied_time_when +
 			dirtytime_expire_interval * HZ))) {
 		trace_writeback_lazytime(inode);