ASoC: wm_adsp: Fix BUG_ON() and WARN_ON() usages

This patch does:
- Move the sanity check with WARN_ON() in wm_adsp_region_to_reg() and
  remove the checks in the callers,
- Fix wrong WARN_ON() usages, replaced with WARN(),
- Fix unreachable or wrong BUG_ON() usages and replace with WARN_ON().

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Reviewed-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie@linaro.org>