arch-riscv: Ignore sched_yield syscall in SE mode

Change-Id: I14f22c06eb8fdbe063980b4cd0a49387b9113a97
Reviewed-on: https://gem5-review.googlesource.com/6961
Maintainer: Brandon Potter <Brandon.Potter@amd.com>
Reviewed-by: Alec Roelke <ar4jc@virginia.edu>
1 file changed