ASoC: Parse board ID/revision information from WM1250-EV1 board

The WM1250-EV1 board has an ID chip on it, check the board ID and display
the board revision during startup.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Liam Girdwood <lrg@ti.com>