Use ASSERT0P() to check that a pointer is NULL.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Kay Pedersen <mail@mkwg.de>
Reviewed-by: Alexander Motin <mav@FreeBSD.org>
Signed-off-by: Dag-Erling Smørgrav <des@FreeBSD.org>
Closes openzfs#15225

module/zfs/dbuf.c

@@ -2701,7 +2701,7 @@ dmu_buf_will_clone(dmu_buf_t *db_fake, dmu_tx_t *tx)
 	 */
 	mutex_enter(&db->db_mtx);
 	VERIFY(!dbuf_undirty(db, tx));
-	ASSERT3P(dbuf_find_dirty_eq(db, tx->tx_txg), ==, NULL);
+	ASSERT0P(dbuf_find_dirty_eq(db, tx->tx_txg));
 	if (db->db_buf != NULL) {
 		arc_buf_destroy(db->db_buf, db);
 		db->db_buf = NULL;