ASoC: wm5110: Fix PGA clear when disabling DRE

We don't want to use a bypassed write in wm5110_clear_pga_volume,
we might disable the DRE whilst the CODEC is powered down. A
normal regmap_write will always go to the hardware (when not on
cache_only) even if the written value matches the cache. As using
a normal write will still achieve the desired behaviour of bring
the cache and hardware in sync, this patch updates the function
to use a normal write, which avoids issues when the CODEC is
powered down.

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