zephyr: it81302: Enable divide-by-zero exception check
zephyr: it81302: Enable divide-by-zero exception check

Enable the divide-by-zero exception check in the the compiler
for RISCV CPUs.

Without this change:

ec:~$ crash divzero
 ffffffffCommand returned error: 1

With this change:
ec:~$ crash divzero
E:
E:  mcause: 3, Breakpoint
E:   mtval: 0
E:      a0: 00000001    t0: 8010d988
E:      a1: fffffffe    t1: 00000020
E:      a2: 00000000    t2: 00000000
E:      a3: 000000c0    t3: 00000000
E:      a4: 00f02700    t4: 00000001
E:      a5: 00000008    t5: aaaaaaaa
E:      a6: 00000011    t6: aaaaaaaa
E:      a7: 00000000
E:      tp: aaaaaaaa
E:      ra: 80013866
E:    mepc: 8001386a
E: mstatus: 00001880
E:
E: >>> ZEPHYR FATAL ERROR 0: CPU exception on CPU 0
E: Current thread: 0x801063f0 (shell_uart)
E: Halting system

BUG=b:231844211
TEST=crash divzero
BRANCH=none

Signed-off-by: Andrew McRae <44ad1424cfc8411c96d9181798ca41ae55709dfb@google.com>
Cq-Depend: chromium:3637157
Change-Id: I4edf7d5b33d31a39d2172f3b8b1e4becdd94def4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3631725
Reviewed-by: Dino Li <338d523ecf3700bd86eb9c34d220f91911d2a18c@ite.com.tw>
Reviewed-by: Yuval Peress <50dc11c009bd4d7e9d9d15a383c1743ce5ee82ef@google.com>
Reviewed-by: Peter Marheine <ef0b2c492edde94778d7465bfbaeed52c5be6858@chromium.org>

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