mpipl: move from diagnostic target to crash target

The MPIPL function was moved from the diagnostic target to the crash
target. The diagnostic target is now a part of the crash target so it
will still be called as a part of this process.

The following commit has more info on why this change was made:
https://gerrit.openbmc-project.xyz/c/openbmc/openbmc/+/39711



Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: Ie1598a06f5d14edd6edde1e95d63becbd1fdba96