tty: serial: qcom_geni_serial: Don't slow all ports just for kgdb

If you turn on CONFIG_KGDB then you'll get CONFIG_CONSOLE_POLL
selected.

If you have CONFIG_CONSOLE_POLL selected then the GENI serial driver
was setting RX_BYTES_PW to 1 for _all_ UART ports.

This doesn't seem like such a good idea.  Let's only set RX_BYTES_PW
to 1 for the console port.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Reviewed-by: Mukesh Kumar Savaliya <msavaliy@codeaurora.org>
Reviewed-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>