riscv-virtual-memory: Add virtual memory setup

Execution in supervisor level code in RISCV requires early setup of
virtual memory. Add initialization calls in
src/arch/riscv/virtual_memory.c to implement the required page table
setup, and helper functions to use when jumping to the payload correctly
in riscv.

Change-Id: I46e080e0ee8dc13277d567dcd4bf0f61a4507b76
Signed-off-by: Thaminda Edirisooriya <thaminda@google.com>
Reviewed-on: http://review.coreboot.org/11369
Tested-by: build bot (Jenkins)
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
2 files changed