riscv: Remove config string support

The code dealing with the old config string isn't needed anymore,
because the config string has been deprecated in favor of
OpenFirmware-derived devicetrees.

Change-Id: I71398fb4861dbaf7eefc6e6f222bb7159798fafa
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/22594
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
7 files changed