zephyr/test: Add missing header
zephyr/test: Add missing header

Gcc-10 was reporting an implicit declaration of function, include the
header that defines it.

BRANCH=None
BUG=None
TEST=./twister with gcc

Signed-off-by: Jeremy Bettis <4df7b5147fee087dca33c181f288ee7dbf56e022@google.com>
Change-Id: Ic910826da6c8c65c48b6fc6e83b50c77310a65fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/4004760
Auto-Submit: Jeremy Bettis <4df7b5147fee087dca33c181f288ee7dbf56e022@chromium.org>
Tested-by: Jeremy Bettis <4df7b5147fee087dca33c181f288ee7dbf56e022@chromium.org>
Reviewed-by: Madhu P <91daf3dcb52497aaee2bfb2e83426acf7b0e812c@google.com>
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>
Commit-Queue: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@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