core/host: Add implementation for host panic
core/host: Add implementation for host panic

panic_set_reason() and panic_get_reason() are called from
system_common_pre_init() if CONFIG_SOFTWARE_PANIC is enabled. A followup
commit removes CONFIG_SOFTWARE_PANIC since all boards enable it, so we
need stub implementations for the host in order to successfully compile.

LOW_COVERAGE_REASON=legacy code
BRANCH=none
BUG=none
TEST=make buildall

Signed-off-by: Tom Hughes <fc5c12f30a5ed2baa0581f44ee14ad1eb7b20d83@chromium.org>
Change-Id: I33322b593f707f3c8937f4a7cd2189841b197aa1
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3935024
Reviewed-by: Daisuke Nojiri <fd5f93af191bf7e8f73ea71cc3c0f66b41b1dd49@chromium.org>
Code-Coverage: Zoss <345cf107e82c70959d46f59d98bddc98ce458aff@prod.google.com>

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