zephyr: test default implementation of charge_port_is_connected
zephyr: test default implementation of charge_port_is_connected

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: Ia600437085eef5133442477dc4617036870ddbca
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3513659
Reviewed-by: Sam Hurst <500b4cddcd66abe3fe333e92c4c95d7f41e62e4e@google.com>

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