ASoC: gtm601: add Broadmobi bm818 sound profile

The Broadmobi bm818 uses stereo sound at 48Khz sample rate

Signed-off-by: Angus Ainslie (Purism) <angus@akkea.ca>
Link: https://lore.kernel.org/r/20191223154712.18581-2-angus@akkea.ca


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