inode: rename i_wb_list to i_io_list

There's a small consistency problem between the inode and writeback
naming. Writeback calls the "for IO" inode queues b_io and
b_more_io, but the inode calls these the "writeback list" or
i_wb_list. This makes it hard to an new "under writeback" list to
the inode, or call it an "under IO" list on the bdi because either
way we'll have writeback on IO and IO on writeback and it'll just be
confusing. I'm getting confused just writing this!

So, rename the inode "for IO" list variable to i_io_list so we can
add a new "writeback list" in a subsequent patch.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Josef Bacik <jbacik@fb.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Tested-by: Dave Chinner <dchinner@redhat.com>
diff --git a/fs/internal.h b/fs/internal.h
index ee1209c..71859c4d 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -118,7 +118,7 @@
 /*
  * fs-writeback.c
  */
-extern void inode_wb_list_del(struct inode *inode);
+extern void inode_io_list_del(struct inode *inode);
 
 extern long get_nr_dirty_inodes(void);
 extern void evict_inodes(struct super_block *);