Always return exit code 0 when cmd_uart_read stopped reading
data from UART. Instead, return with a error code in case
reading from the UART interface failed.
Currently, this command might return with exit code -1 because
uart_poll_in didn't return data and the read duration expired.
Signed-off-by: Daniel Schultz <d.schultz@phytec.de>
This command waits for a given time (in seconds) and will continuously
poll from the UART device and print on the Shell console. This command
can be used to also test the RX line.
Signed-off-by: Daniel Schultz <d.schultz@phytec.de>
