servo_v4: Tie data role preference to DTS mode setting
servo_v4: Tie data role preference to DTS mode setting

When servo_v4 acts as a debug test system (DTS) its expected use
case is for triggering CCD mode and Faft testing. To that end, its
desired default data role is to be a UFP so that the enet and USB
port are accessible by the DUT.  However, when servo is acting a
regular SRC port, it makes more sense for the data role pairing to
be consistent with a normal SRC port device which is SRC/DFP.

BUG=b:64720447
BRANCH=servo
TEST=Tested with Eve using twinkie USB PD analyzer. Verified that when
DTS mode is enabled a data role swap request is sent to the DUT and
when DTS mode is disabled that servo_v4 does not send a data role swap
request.

Change-Id: I071f85fc99f1c877d86ef48ec7fa38d6850d5679
Signed-off-by: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@google.com>
Reviewed-on: https://chromium-review.googlesource.com/615813
Commit-Ready: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@chromium.org>
Tested-by: Scott Collyer <7d40b3eb9e17bf55d972074a5e77a7ea4159f9dd@chromium.org>
Reviewed-by: Nick Sanders <f4566bb3c90c0bf5fa0906b296b1da45051a62ee@chromium.org>

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