ASoC: wm9713: convert to regmap

Convert the Wolfson WM9713 to regmap API. This will leverage all the
regmap functions (debug, registers update, etc ...).

As a bonus, this will pave the path to gpio chip introduction, and
devicetree support. This was tested on the mioa701 board, pxa27x based,
in PCM playback, and through suspend/resume.

Signed-off-by: Robert Jarzmik <robert.jarzmik@free.fr>
Reviewed-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>