PHAL: Add service dependency to DEVTREE creation

Start the services that require DEVTREE after the
openpower-update-bios-attr-table.service since that's the one that
sets up the DEVTREE symlink. Also update the path to DEVTREE to the one
defined by the meson options.

Tested: Verified phal started after the bios attr service file, powered
on, and issued reboot at power on without any errors. Verified service
files had devtree path of:
Environment="PDBG_DTB=/media/hostfw/running/DEVTREE"

Signed-off-by: Adriana Kobylak <anoo@us.ibm.com>
Change-Id: If41f86b287b70c48d17c6f4b2af9aa0adfb81488
diff --git a/service_files/op-stop-instructions@.service.in b/service_files/op-stop-instructions@.service.in
index af5646e..2eaee19 100644
--- a/service_files/op-stop-instructions@.service.in
+++ b/service_files/op-stop-instructions@.service.in
@@ -5,6 +5,7 @@
 Wants=obmc-host-stopping@%i.target
 Before=obmc-host-stopping@%i.target
 After=op-occ-disable@%i.service
+After=openpower-update-bios-attr-table.service
 Conflicts=obmc-host-startmin@%i.target
 ConditionPathExists=/sys/class/fsi-master/fsi0/slave@00:00/cfam_id
 ConditionPathExists=!/run/openbmc/mpreboot@%i