ASoC: arizona: Implement stability check for LHPF coefficients

ASoC: arizona: Implement stability check for LHPF coefficients

Specifying unstable coefficients for the low/high pass filters can have
a severe impact on the audio. This patchs adds a stability check on the
coefficients written to the low/high pass filter block to prevent this.

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