ASoc: wm8731: add 32bit mode.

commit cf5ef3a2 upstream.

This patch adds 32 bit word capability to the wm8731 driver. The wm8731
codec is capable of handling 32 bit word sizes, however that has not
previously been activated in the codec driver.

Signed-off-by: Matt Flax <flatmax@flatmax.org>
Acked-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@kernel.org>