charger: Prevent SET access to EC_CMD_CHARGE_STATE on locked systems
charger: Prevent SET access to EC_CMD_CHARGE_STATE on locked systems

The SET sub-command of EC_CMD_CHARGE_STATE sets charger current /
voltage parameters to arbitrary values and should be locked down.
EC_CMD_CHARGE_CONTROL, on the other hand, switches between several safe
operation modes, and should be allowed.

BUG=None
TEST=On kevin, set force_locked, plug zinger, and verify:
ectool chargestate param 4 3 <-- ACCESS_DENIED
ectool chargestate show <-- prints params
ectool chargecontrol idle <-- stops charging battery
ectool chargecontrol normal <-- battery charges again
BRANCH=None

Signed-off-by: Shawn Nematbakhsh <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Change-Id: I5503f07bb196d023a9bcd2e33f2e247f061f05e5
Reviewed-on: https://chromium-review.googlesource.com/757237
Commit-Ready: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Tested-by: Shawn N <5259333ce42e3ace6a73988cec7115ed9d3a661a@chromium.org>
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

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