ASoC: wm_adsp: Remove len field from wm_adsp_alg_region

The algorithm region information in the firmware doesn't contain a
length field, explicitly pass this to the create_control function rather
than bundling into wm_adsp_alg_region.

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