ASoC: sgtl5000: add 5 band graphic equalizer

Enable 5-band graphic equalizer which allows manipulation of
gain in range -11.75dB to 12dB for 5 specific sound bands:
115Hz, 330Hz, 990Hz, 3000Hz, 9900Hz.

Signed-off-by: Michal Oleszczyk <oleszczyk.m@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>