TCPMV2: check if vconn swap is allowed
TCPMV2: check if vconn swap is allowed

Connect TBT/USB4 device to PD port in G3 state, port discovery requests
to be vconn source even the PP5000_A rail is turned off in G3, as a
result system won't be able to source vconn and cable discovery fails.

Port discovery should check if sourcing vconn is possible at board
level before it requests swap vconn so to prevent this failure.

BUG=b:198226223
BRANCH=none
TEST=Boot up ADL RVP, put system in G3 by "shutdown -h now", plug in
Gatkex board to port 0, confirmed EC does not request vconn swap in
G3 if 5V is not available. Wake up system by "powerbtn" on EC console,
cable discovery is successful.

Signed-off-by: li feng <0fd15d95d647a38d004d7ac9a3d0587bb1c98551@intel.com>
Change-Id: Ic94c21dbfe0c910b6c9826302b8658eeeff44b72
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3131408
Reviewed-by: Vijay Hiremath <006c712879a3af08bfdb5c2b8491a8b2d5fd73cd@intel.com>
Reviewed-by: Abe Levkoy <2e1ad7039298f93262cf06bbb457275fb3e2ecb5@chromium.org>
Commit-Queue: Abe Levkoy <2e1ad7039298f93262cf06bbb457275fb3e2ecb5@chromium.org>

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