3006 VERIFY[S,U,P] and ASSERT[S,U,P] frequently check if first argument is zero

@@ -326,11 +326,11 @@
                 ASSERT3U(db->db.db_size, >=, dn->dn_bonuslen);
                 ASSERT3U(db->db.db_offset, ==, DMU_BONUS_BLKID);
         } else if (db->db_blkid == DMU_SPILL_BLKID) {
                 ASSERT(dn != NULL);
                 ASSERT3U(db->db.db_size, >=, dn->dn_bonuslen);
-                ASSERT3U(db->db.db_offset, ==, 0);
+                ASSERT0(db->db.db_offset);
         } else {
                 ASSERT3U(db->db.db_offset, ==, db->db_blkid * db->db.db_size);
         }
 
         for (dr = db->db_data_pending; dr != NULL; dr = dr->dr_next)

@@ -2306,11 +2306,11 @@
          */
         if (db->db_blkid == DMU_BONUS_BLKID) {
                 dbuf_dirty_record_t **drp;
 
                 ASSERT(*datap != NULL);
-                ASSERT3U(db->db_level, ==, 0);
+                ASSERT0(db->db_level);
                 ASSERT3U(dn->dn_phys->dn_bonuslen, <=, DN_MAX_BONUSLEN);
                 bcopy(*datap, DN_BONUS(dn->dn_phys), dn->dn_phys->dn_bonuslen);
                 DB_DNODE_EXIT(db);
 
                 if (*datap != db->db.db_data) {

@@ -2505,11 +2505,11 @@
         blkptr_t *bp = zio->io_bp;
         blkptr_t *bp_orig = &zio->io_bp_orig;
         uint64_t txg = zio->io_txg;
         dbuf_dirty_record_t **drp, *dr;
 
-        ASSERT3U(zio->io_error, ==, 0);
+        ASSERT0(zio->io_error);
         ASSERT(db->db_blkptr == bp);
 
         if (zio->io_flags & ZIO_FLAG_IO_REWRITE) {
                 ASSERT(BP_EQUAL(bp, bp_orig));
         } else {