ASoC: atmel-soc: make it buildable on other architectures

Not very useful on non AT91/AVR32 platforms but it provides
more build coverage and prepares for ARM multiplatform.

Also fixes a couple of format type warnings.

Signed-off-by: Joachim Eastwood <manabian@gmail.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>