bcachefs: Fix fiemap (again)

when iterating over reflink pointers, we use the key we just emitted to
set the iterator position - which means we have to be setting the key's
inode field as well
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/fs.c

@@ -1249,7 +1249,8 @@ static int bch2_fiemap(struct inode *vinode, struct fiemap_extent_info *info,
 					   offset_into_extent),
 				       &cur.k);
 		bch2_key_resize(&cur.k.k, sectors);
-		cur.k.k.p.offset = iter->pos.offset + cur.k.k.size;
+		cur.k.k.p = iter->pos;
+		cur.k.k.p.offset += cur.k.k.size;
 
 		if (have_extent) {
 			ret = bch2_fill_extent(c, info,