An errata exists for cs47l15 where the reset must be handled
differently and removed before DCVDD is applied. A soft reset is used
for situations where a reset is required to reset state. This does
however, make this part unsuitable for DCVDD supplies with a rise time
greater than 2mS.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>