ARM: pia335x: added headerfile with board IDs for piA-AM335x boards. Added board id detection.

Signed-off-by: Marian Lüder <m.lueder@pironex.de>
ARM: pia335x: audio: initialisation now depends on board ID

Signed-off-by: Marian Lüder <m.lueder@pironex.de>