ASoC: rt1015: add rt1015 amplifier driver

This is initial amplifier driver for rt1015.

Signed-off-by: Jack Yu <jack.yu@realtek.com>
Link: https://lore.kernel.org/r/20200115112519.22050-1-jack.yu@realtek.com


Signed-off-by: Mark Brown <broonie@kernel.org>