btrfs: Remove unused -EIO assignment in end_bio_extent_readpage

In case we hit the error case for a metadata buffer in
end_bio_extent_readpage then 'ret' won't really be checked before it's
written again to. This means the -EIO in this case will never be
checked, just remove it.

Fixes-coverity-id: 1442513
Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/extent_io.c

@@ -2614,8 +2614,6 @@ static void end_bio_extent_readpage(struct bio *bio)
 			if (test_and_clear_bit(EXTENT_BUFFER_READAHEAD,
 					       &eb->bflags))
 				btree_readahead_hook(eb, -EIO);
-
-			ret = -EIO;
 		}
 readpage_ok:
 		if (likely(uptodate)) {