armh: employ control feature

As 50-sudo-su script cares for sudo and su control facilities no more
that hook is aptly renamed to 50-sshd-root (should be generalized
either some day).

features.in/armh/config.mk

@@ -1,2 +1,2 @@
-use/armh:
+use/armh: use/control/sudo-su
 	@$(call add_feature)

features.in/armh/rootfs/image-scripts.d/50-sshd-root

@@ -2,9 +2,6 @@
 # poor man's root switch
 # NB: 50-users creates predefined users
 
-control su public
-control sudo public
-
 cat >> /etc/openssh/sshd_config << EOF
 PermitRootLogin yes
 UseDNS no