[media] docs: fix typo in lirc_device_interface.xml

<para>The data written to the chardev is a pulse/space sequence of integer

values. Pulses and spaces are only marked implicitly by their position. The

data must start and end with a pulse, therefore, the data must always include

an unevent number of samples. The write function must block until the data has

an uneven number of samples. The write function must block until the data has

been transmitted by the hardware.</para>

</section>