beaglelogic: Add beaglelogic_tcp_drain function

beaglelogic: Add beaglelogic_tcp_drain function

The function drains off all the remaining data in the receive socket
and is triggered before starting a capture and after a capture is
completed. In the absence of this function, there is a possibility of
data corruption and also the NodeJS TCP server throws an error if the
buffer is not completely read out before the socket is closed.

Signed-off-by: Kumar Abhishek <redacted>