usbc: turn on/off vconn appropriately
usbc: turn on/off vconn appropriately

- Ensure that Vconn does not turn off during a power role swap either
way
- Reduce the amount of time we wait for power supply and vconn power to
be ready to the maximum of either (instead of adding their delays)
- Drop unnecessary VCONN conditionals

BRANCH=none
BUG=none
TEST=builds

Change-Id: Ic1d43351e3407c246159570559de3588ee685640
Signed-off-by: Jett Rink <9d4aef0593e6843318d99df31597fb6153b89787@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1825505
Reviewed-by: Sam Hurst <500b4cddcd66abe3fe333e92c4c95d7f41e62e4e@google.com>
Reviewed-by: Denis Brockus <6b21e8190fb5e373363fb95271367073a16474ef@chromium.org>

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