zephyr: allow only one power sequencing option via kconfig
zephyr: allow only one power sequencing option via kconfig

PLATFORM_EC_POWERSEQ and AP_PWRSEQ implement the same subsystem, so
update the kconfig to prevent both from being enabled at the same time.

BUG=b:233681784
TEST=zmake testall
BRANCH=none

Signed-off-by: Peter Marheine <ef0b2c492edde94778d7465bfbaeed52c5be6858@chromium.org>
Change-Id: Ied6ffdd8b541acb343ac4e36ea901f9d252717c5
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3703088
Reviewed-by: Keith Short <f6d578f97033c25f1206cb57d52f358974c82954@chromium.org>

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