greybus: uart: Relocate UART parity/overrun/framing/break signals

Parity/overrun/framing and break signals have been moved to the
receive-data message to more easily associate the signals with the TTY API.
Update the definitions in the protocol header and add a flags field to the
receive-data structure to facilitate transmission of those signal with the
receive-data message.

Signed-off-by: Bryan O'Donoghue <bryan.odonoghue@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>