TCPMv2 PE: Remove PE_DO_PORT_DISCOVERY
TCPMv2 PE: Remove PE_DO_PORT_DISCOVERY

Remove state, functions, and fields. Previous changes removed usage of
this state, so this is a non-functional change.

BUG=b:158572770
BUG=b:155890183
BUG=b:155890456
BUG=b:155891305
BUG=b:152419850
TEST=make buildall
BRANCH=none

Change-Id: I6db07fb8b77126f8c214d07f899cf510fca8aa8a
Signed-off-by: Abe Levkoy <2e1ad7039298f93262cf06bbb457275fb3e2ecb5@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2238535
Reviewed-by: Diana Z <cb2016afc7183e5356c690dc63b4ba817470501a@chromium.org>

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