aaf: Add support for direct read/write transfers

aaf: Add support for direct read/write transfers

This patch adds support for direct read/write transfers (i.e. mmap
access mode) to the AAF plugin.

In order to enable direct read/write transfers, the AAF plugin is
required to implement ioplug's pseudo mmap mode. In this mode, the audio
buffer management (e.g. areas allocation, clean up, and data copy) is
handled at upper layers, making the AAF plugin simpler. So this patch
removes all code related to audio buffer management as well as the
transfer() callback from the AAF plugin.

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