core/riscv-rv32i: add atomic_inc and atomic_dec
core/riscv-rv32i: add atomic_inc and atomic_dec

BRANCH=none
BUG=b:146213943
TEST=make BOARD=asurada_scp

Signed-off-by: Tzung-Bi Shih <5e6f7578cd434ae5b4c9ffe5250f7a87a25045d7@chromium.org>
Change-Id: I3d87c9906df1b631fa3733eeae92d356ec287611
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2275710
Reviewed-by: Dino Li <338d523ecf3700bd86eb9c34d220f91911d2a18c@ite.com.tw>
Reviewed-by: Eric Yilun Lin <2f2733c7206ea2b76bd2db1905cc5e8a75841c48@chromium.org>

coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec,coreboot/chrome-ec