tty: serial: qcom_geni_serial: Add comments for clarification

* Document reason for newline character counting in console_write
* Document reason for disabling IRQ in the system resume operation

Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>
Reviewed-by: Matthias Kaehlcke <mka@chromium.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>