nmi: Use libpdbg directly

This avoids calling DBus to run a systemd unit that is effectively a
shell script when we already have libpdbg on the system anyway.

Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
Change-Id: I9a36c38f075d402b9bc406433475a371d1cdbe62
diff --git a/Makefile.am b/Makefile.am
index 1280311..d9760ca 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -2,8 +2,7 @@
 
 systemdsystemunit_DATA = \
   pcie-poweroff@.service \
-  xyz.openbmc_project.Control.Host.NMI.service \
-  nmi.service
+  xyz.openbmc_project.Control.Host.NMI.service
 
 bin_PROGRAMS = \
 	openpower-proc-control \