aaf: Implement Capture mode support

aaf: Implement Capture mode support

This patch implements the capture mode support from the AAF plugin.
Simply put, this mode works as follows: AVTPDUs are received from the
network, the PCM samples are retrieved and presented to the alsa-lib
layer at the presentation time. In summary, the capture mode implements
a typical AVTP Listener.

Once the AAF device is put in running state, packet reception is
started. Every time an AVTPDU is received, the plugin checks if it is
valid (according to the stream configuration provided by the user) and
copies the PCM samples to the audio buffer. Note that at this moment,
the samples are not presented to the alsa-lib layer yet (i.e. hw_ptr is
not incremented).

The media clock starts at the presentation time from the first AVTPDU.
At every tick from the media clock, PCM samples are presented to the
alsa-lib layer.

Below follows some secondary discussion about this patch:

The functions aaf_mclk_start_playback() and aaf_mclk_start_capture()
have some common code. This patch does some code refactoring so the
common code is put in a new function (aaf_mclk_start) which is called
by both aaf_mclk_start_playback() and aaf_mclk_start_capture().

Also, the helper function aaf_inc_hw_ptr() is refactored so it can be
used to increment both aaf->hw_ptr and aaf->hw_virt_ptr.

Signed-off-by: Andre Guedes <andre.guedes@intel.com>
Signed-off-by: Jaroslav Kysela <perex@perex.cz>