Prune /*NOTREACHED*/

This includes a simplification of mkbusy and format correctness in zhack
and ztest

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ahelenia Ziemiańska <nabijaczleweli@nabijaczleweli.xyz>
Issue #12201

module/os/freebsd/zfs/zfs_ctldir.c

@@ -1084,7 +1084,7 @@ zfsctl_snapdir_readdir(struct vop_readdir_args *ap)
 		}
 		zfs_uio_setoffset(&uio, cookie + dots_offset);
 	}
-	/* NOTREACHED */
+	__builtin_unreachable();
 }
 
 static int

module/zfs/zfs_log.c

@@ -79,7 +79,6 @@ zfs_log_create_txtype(zil_create_t type, vsecattr_t *vsecp, vattr_t *vap)
 			return (TX_CREATE_ACL);
 		else
 			return (TX_CREATE_ATTR);
-		/*NOTREACHED*/
 	case Z_DIR:
 		if (vsecp == NULL && !isxvattr)
 			return (TX_MKDIR);