greybus: interface: fix broken UniPro flow control

A recent commit inadvertently disabled E2EFC on all interface
connections, due to a failure to clear the ES3 bootrom quirk flags
during mode switch.

Testing Done: Verified that the CPort flags are again set to 0x7 for
non-bootrom interface connections.

Fixes: 5b638080e94e ("svc: keep interfaces registered during
mode switch")
Signed-off-by: Johan Hovold <johan@hovoldconsulting.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>