greybus: uart: Add support for UART error signals

After reviewing the UART specification for greybus break, parity, framing
and over-run errors were moved to the receive-data message. This patch
implements that specification change in the UART protocol driver. Matching
code in gbsim has been tested with this change.

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