Set minimum priority for PCIe scan

Set the Nice score to the maximum (lowest priority) so that it
doesn't interfere with other services when scanning for PCIe
devices.

Tested:
Confirmed that the PCIe device list still loads in Redfish.

Change-Id: Ic13c028940fb5d9491a327b5c2342c36c5c581b1
Signed-off-by: Jason M. Bills <jason.m.bills@intel.com>
diff --git a/service_files/xyz.openbmc_project.PCIe.service b/service_files/xyz.openbmc_project.PCIe.service
index 7c48a03..1d38eb4 100644
--- a/service_files/xyz.openbmc_project.PCIe.service
+++ b/service_files/xyz.openbmc_project.PCIe.service
@@ -5,6 +5,7 @@
 Restart=always
 ExecStart=/usr/bin/peci-pcie
 Type=simple
+Nice=19
 
 [Install]
 WantedBy=multi-user.target