ASoC: alc5632: Fix Boost Volume TLVs used for the external microphones

This brings the TLVs in sync with the documentation and allows to properly
manipulate mic boost controls with alsamixer.

Signed-off-by: Paul Fertser <fercerpav@gmail.com>
Signed-off-by: Leon Romanovsky <leon@leon.nu>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>