bcachefs: Don't use extent_ptr_decoded_append() in write path (fixup patch)

bch2_extent_ptr_decoded_append() is more general than we need here; we
know we're initializing a new extent so e.g. we're going to need the crc
entry.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/io.c

@@ -631,10 +631,12 @@ static void init_append_extent(struct bch_write_op *op,
 			       struct bversion version,
 			       struct bch_extent_crc_unpacked crc)
 {
-	struct bkey_i_extent *e = bkey_extent_init(op->insert_keys.top);
+	struct bkey_i_extent *e;
 	struct bch_extent_ptr *ptr;
 
 	op->pos.offset += crc.uncompressed_size;
+
+	e = bkey_extent_init(op->insert_keys.top);
 	e->k.p		= op->pos;
 	e->k.size	= crc.uncompressed_size;
 	e->k.version	= version;