ASoC: wm2200: Map DSPs into regmap

Use the regmap ranges support to add the WM2200 DSP core memory pages
into the "register map" beyond the end of the real register map. We
don't extend beyond 16 bits since the regmap API will iterate over
every register doing diagnostics.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>