what to use for DTO instead of /sys/devices/bone_capemgr?

I used to configure the IO pins with my custom DTO like this:

  SYSTEM_CK ("dtc -O dtb -o DM-GPIO-HWM-00A0.dtbo -b 0 -@ DM-GPIO-HWM.dts");
  SYSTEM_CK ("cp DM-GPIO-HWM-00A0.dtbo /lib/firmware/");
  SYSTEM_CK ("echo DM-GPIO-HWM >/sys/devices/bone_capemgr.9/slots");

After flashing to the latest image
(bone-debian-8.4-lxqt-4gb-armhf-2016-05-13-4gb.img) and an apt-get upgrade,
this no longer works: the third command faile because
/sys/devices/bnoe_capemgr.9/slots no longer exists.

Unfortunately I didn't check before the apt-get upgrade. I found some stuff
that makes it look like this probably isn't the problem though.

What should I be looking for to get the third command or something equivalent
working again?