ASoC: core: Add new SOC_DOUBLE_SX_TLV macro

Currently macros only exist for SX style (implicit sign bit 2's
compliment) volume controls where the volumes for left and right
are in separate registers. Some future Cirrus devices will have
both volumes in the same register, as such add a new macro to
support this.

Signed-off-by: Charles Keepax <ckeepax@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20220621102041.1713504-4-ckeepax@opensource.cirrus.com


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