spi-mux: do not set if chassis power is on

The op-reset-chassis-running@.service determines if chassis power is on,
and if so creates the /run/openbmc/chassis@0-on file. Need to let this
service run and create the file if chassis power is on.

Tested:
- Verified that when BMC is rebooted with chassis power on that when
  the BMC comes back up, it does not run the set-spi-mux.service.

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: I6075008dc8d7be9d111bbbc9b48606d8bb806e63
diff --git a/set-spi-mux.service.in b/set-spi-mux.service.in
index 3236ca5..b8042b5 100644
--- a/set-spi-mux.service.in
+++ b/set-spi-mux.service.in
@@ -1,6 +1,7 @@
 [Unit]
 Description=Set the SPI mux
 ConditionPathExists=!/run/openbmc/chassis@0-on
+After=op-reset-chassis-running@0.service
 After=op-wait-power-off@0.service
 
 [Service]