units: restrict hugepages fs a bit

suid binaries and device nodes should not be placed there, hence forbid
it.

Of all the API VFS we mount from PID 1 or via a unit file this one is
the only one where we didn't add MS_NODEV/MS_NOSUID. Let's address that,
since there's really no reason why device nodes or suid binaries would
be placed in hugetlbfs.

units/dev-hugepages.mount

@@ -21,3 +21,4 @@ ConditionVirtualization=!private-users
 What=hugetlbfs
 Where=/dev/hugepages
 Type=hugetlbfs
+Options=nosuid,nodev