Only set kern.geom.part.mbr.enforce_chs=0 once, instead of once per disk

Sponsored by:	ScaleEngine Inc.

usr.sbin/bsdinstall/scripts/zfsboot

@@ -806,7 +806,6 @@ zfs_create_diskpart()
 	if [ "$ZFSBOOT_FORCE_4K_SECTORS" ]; then
 		align_small="-a 4k"
 		align_big="-a 1m"
-		sysctl kern.geom.part.mbr.enforce_chs=0
 	fi
 
 	case "$ZFSBOOT_PARTITION_SCHEME" in
@@ -1133,6 +1132,7 @@ zfs_create_boot()
 		f_dprintf "$funcname: With 4K sectors..."
 		f_eval_catch $funcname sysctl "$SYSCTL_ZFS_MIN_ASHIFT_12" \
 		    || return $FAILURE
+		sysctl kern.geom.part.mbr.enforce_chs=0
 	fi
 	local n=0
 	for disk in $disks; do