arch/riscv: Unify trap return

Change-Id: I9de0c92b3f925e8f4db00d7281222a07db68b2ae
Signed-off-by: Jonathan Neuschäfer <j.neuschaefer@gmx.net>
Reviewed-on: https://review.coreboot.org/21763
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Ronald G. Minnich <rminnich@gmail.com>
2 files changed