zephyr: test default implementation of charge_port_is_sink
zephyr: test default implementation of charge_port_is_sink

Add a test for the default implementation which always return 1.

BRANCH=none
BUG=b:222630005
TEST=zmake test test-drivers

Signed-off-by: Yuval Peress <50dc11c009bd4d7e9d9d15a383c1743ce5ee82ef@google.com>
Change-Id: I8edc629353b8e62f40687234682e0de22dc9fa29
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3513660
Reviewed-by: Abe Levkoy <2e1ad7039298f93262cf06bbb457275fb3e2ecb5@chromium.org>

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