We had lots of casts that caused warnings when compiling on RISCV. Clean them up. Change-Id: I46fcb33147ad6bf75e49ebfdfa05990e8c7ae4eb Signed-off-by: Ronald G. Minnich <rminnich@gmail.com> Reviewed-on: http://review.coreboot.org/7066 Reviewed-by: Edward O'Callaghan <eocallaghan@alterapraxis.com> Tested-by: build bot (Jenkins) Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>