The documentation unfortunately doesn't match what SiFive uses in their FSBL.
Use the same values as in FSBL to make DDR RAM work.
Change-Id: I844cc41ed197333adeae495e71ea70b4a9603650
Signed-off-by: Philipp Hug <philipp@hug.cx>
Reviewed-on: https://review.coreboot.org/28582
Reviewed-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>