zephyr: kingler: enable CHARGER_DISCHARGE_ON_AC
zephyr: kingler: enable CHARGER_DISCHARGE_ON_AC

We should enable PLATFORM_EC_CHARGER_DISCHARGE_ON_AC
for toolkit charge and discharge test.

BUG=b:222637801
BRANCH=none
TEST=ectool chargecontrol discharge works well

Change-Id: I68354211a44d03274123b6248b7e9393675ac639
Signed-off-by: wen zhang <8717331d0b247e00f80e6ce2b21e839bc7c51990@huaqin.corp-partner.google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3503079
Reviewed-by: Mike Lee <255a368def86bc53ab15e64f578878686d4eb313@huaqin.corp-partner.google.com>
Reviewed-by: Eric Yilun Lin <2f2733c7206ea2b76bd2db1905cc5e8a75841c48@google.com>

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