USB: spcp8x5: remove broken uart-error handling

Remove broken uart-error handling.

This driver appears to implement uart-error handling but does not
receive status interrupts or status information with bulk in transfers.

Instead status was retrieved at open and used to flag only the first
bulk in transfer.

Signed-off-by: Johan Hovold <jhovold@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>