zephyr: drivers: Add unit test for smart discharge
zephyr: drivers: Add unit test for smart discharge

Add unit test of setting smart discharge zones using host command. Test
if generic board_system_is_idle() recognizes smart discharge zones
correctly.

BUG=b:206903370
BRANCH=none
TEST=zmake configure --test zephyr/test/drivers

Signed-off-by: Tomasz Michalec <a547db31280d14f095c760a23a7523d0b1e55fe6@semihalf.com>
Change-Id: Ia8e8f9a33183fc0bf6ed4f6705c96e86e4f1ef5d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3302214
Tested-by: Tomasz Michalec <c064a6042954d4ba0805003dc021b76413ff1548@google.com>
Commit-Queue: Tomasz Michalec <c064a6042954d4ba0805003dc021b76413ff1548@google.com>
Reviewed-by: Fabio Baltieri <1c55e39c05d9ab42261288cf330256b2af6ba179@google.com>

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