OpenBMC commands for interacting with Cronus

[Matt Spinler]

As part of issue 1178, I added some new services to allow users to put 
the system into a mode that the cronus tool can run.

Here's the summary:

systemctl start obmc-power-chassis-on at 0.target

     * Just power on a system and not start the SBE


systemctl stop host-failure-reboots at 0.service

     * Turns off automatic reboots on checkstops and watchdog timeouts, 
though the BMC will still go to quiesced state.

     * Reboots get enabled again on a BMC reset

     * Can also enable again by starting the service


systemctl start fsi-disable.service

     * Unbinds the FSI driver, and switches the GPIOs for external 
cronus use

     * Do this any time after power on

     * Will need to do this each power on, as the act of powering on 
requires FSI for the VCS workaround


systemctl start fsi-enable.service

     *  Loads the BMC's FSI Driver again

     * A power cycle will also load the drivers


Outstanding issues:

     *  #1397: Switch back to synchronous FSI clocks after unbinding the 
FSI driver

     * #1396:  For Zaius, some services need to be moved under the 
obmc-power-chassis-on at 0.target target