mb/ocp/tiogapass: use IPMI driver functionality for "POST complete"
Replace the mainboard-specific code for "POST complete" signalling with
devicetree entries for using the newly introduced IPMI driver
functionality.
Test: Boot the machine via the BMC web interface and check that sensors
get read correctly by the IPMI firmware when the payload starts.
Change-Id: I7503dec4e72810db8dfe74f72638b466a3d66748
Signed-off-by: Michael Niewöhner <foss@mniewoehner.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48671
Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>