Eve,Gru,Poppy,Reef: forbid DR_SWAP in RO firmware.

Currently, when we jump from RO to RW, we forget our USB PD state.
To recover from this, we send a SOFT_RESET (resetting the counters...),
then either the USB PD partner is happy about it and we can continue,
or it will issue a HARD_RESET to recover from our mismatched vision of
the current connection (e.g wrong role) resulting in a reset of VBUS.

The following use-case is still problematic:
if the system is not write-protected (ie it does USB PD negotiation in
RO EC) and we have no battery (or fully drained-one) as buffer, when we
are connected to a PD power supply, if it issues the HARD_RESET
mentioned above, we are going to brown-out.
It's happening with power-supplies supporting DR_SWAP, the RO EC will
negotiate a power-contract (as a sink), then try to reverse data role
(from UFP to DFP) to identify the power-supply. We end-up being
Sink/DFP, then when we sysjump to RW, we reset roles and send the
SOFT_RESET as Sink/DFP, the power-supply identifies the incorrect data
role and issues the HARD_RESET browning us out.
As a workaround, now we never ask for the DR_SWAP in RO firmware and
stays Sink/UFP.
This is not affecting regular write-protected machines (which are not
doing USB PD in RO EC). For developers, we are no longer doing the
DR_SWAP in RO mode, this is mostly innocuous for a regular power-supply,
but this would break the docking use-case. Normally, we will do it as
soon as we have jumped to RW, so the dock should still work unless the
developer is using the machine with RO EC (eg EC development with
soft-sync disabled).

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>

BRANCH=reef
BUG=b:35648282
TEST=Boot Snappy without battery. Verify RO image doesn't swap
data roles and soft reset issued by RW image as SNK/UFP is
accepted by the HP adapter.

Change-Id: Id184f0d24a006cd46212d04ceae02f640f5bda65
Reviewed-on: https://chromium-review.googlesource.com/461142
Commit-Ready: Daisuke Nojiri <dnojiri@chromium.org>
Tested-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
Reviewed-by: Sam Hurst <shurst@google.com>

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