units: drop /sys/kernel/config automount unit

The mount point directory /sys/kernel/config is only created after the
module is loaded, hence there's little value in having this an automount
unit: the runtime penalty for mounting an autofs here should be the same
as for a real mount.

units/sys-kernel-config.mount

@@ -6,8 +6,10 @@
 #  (at your option) any later version.
 
 [Unit]
-Description=Config File System
+Description=Configuration File System
 DefaultDependencies=no
+ConditionPathExists=/sys/kernel/config
+After=systemd-modules-load.service
 
 [Mount]
 What=configfs