Add AACI audio playback support to the ARM Versatile/PB platform

This driver emulates the ARM AACI interface (PL041) connected to a LM4549 codec.
It enables audio playback for the Versatile/PB platform.

Limitations:
- Supports only a playback on one channel (Versatile/Vexpress)
- Supports only one TX FIFO in compact-mode or non-compact mode.
- Supports playback of 12, 16, 18 and 20 bits samples.
- Record is not supported.
- The PL041 is hardwired to a LM4549 codec.

Versatile/PB test build:
linux-2.6.38.5
buildroot-2010.11
alsa-lib-1.0.22
alsa-utils-1.0.22
mpg123-0.66

Qemu host: Ubuntu 10.04 in Vmware/OS X

Playback tested successfully with speaker-test/aplay/mpg123.

Signed-off-by: Mathieu Sonet <contact@elasticsheep.com>
[Peter Maydell: fixed typo in code clearing SL1RXBUSY/SL2RXBUSY
 bits, as spotted by Andrzej Zaborowski]
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Andrzej Zaborowski <andrew.zaborowski@intel.com>
