riscv: use new-style CBFS header lookup

We recently restructured where the CBFS header is stored
and how it is looked up, with less magic. The RISC-V port
didn't get the memo, so have it follow the pack now.

Change-Id: Ic27e3e7f9acd55027e357f2c4beddf960ea02c4d
Signed-off-by: Patrick Georgi <patrick@georgi-clan.de>
Reviewed-on: http://review.coreboot.org/9795
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>
Tested-by: build bot (Jenkins)
2 files changed