Remove spurious $flags; it's a paste-o from copying the line from rc.subr.

Also, add a comment documenting the args passed to mount_md().

etc/rc.initdiskless

@@ -197,8 +197,9 @@ handle_remount() { # $1 = mount point
 
 # Create a generic memory disk.
 # The 'auto' parameter will attempt to use tmpfs(5), falls back to md(4).
+# $1 is size in 512-byte sectors, $2 is the mount point.
 mount_md() {
-    /sbin/mdmfs $flags -s $1 auto $2
+    /sbin/mdmfs -s $1 auto $2
 }
 
 # Create the memory filesystem if it has not already been created