The input PGAs have a gain range from -17.25dB to +30dB in 0.75dB steps.

The boost stage can provide additional gain. For line inputs, -12dB to
+6dB gain is available on the boost mixer. For micphone inputs, it can
provide up to +29dB additional gain from the microphone PGA.
Signed-off-by: NZidan Wang <zidan.wang@freescale.com>
Acked-by: NCharles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: NMark Brown <broonie@kernel.org>