bcachefs: Fix uninitialized var warning

Can't actually be used uninitialized, but gcc was being silly.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/backpointers.c

@@ -690,7 +690,7 @@ static int check_extent_to_backpointers(struct btree_trans *trans,
 
 	ptrs = bch2_bkey_ptrs_c(k);
 	bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
-		struct bpos bucket_pos;
+		struct bpos bucket_pos = POS_MIN;
 		struct bch_backpointer bp;
 
 		if (p.ptr.cached)

fs/bcachefs/buckets.c

@@ -1134,7 +1134,7 @@ static int __trigger_extent(struct btree_trans *trans,
 	r.e.nr_required	= 1;
 
 	bkey_for_each_ptr_decode(k.k, ptrs, p, entry) {
-		s64 disk_sectors;
+		s64 disk_sectors = 0;
 		ret = bch2_trigger_pointer(trans, btree_id, level, k, p, entry, &disk_sectors, flags);
 		if (ret < 0)
 			return ret;