ASoC: max98390: Added Amplifier Driver

This is the initial amplifier driver for max98390.

Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Steve Lee <steves.lee@maximintegrated.com>
Link: https://lore.kernel.org/r/20200518005038.21074-1-steves.lee@maximintegrated.com


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