riscv-trap-handling: Add implementation for trap calls in riscv

RISCV requires the bios/bootloader to set up an interface by which it
can get information about memory, talk to host devices, etc. Put
implementation for spike in
src/mainboard/emulation/spike-riscv/spike_util.c, and

Change-Id: Ie1d5f361595e48fa6cc1fac25485ad623ecdc717
Signed-off-by: Thaminda Edirisooriya <thaminda@google.com>
Reviewed-on: http://review.coreboot.org/11368
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
7 files changed