Some systems may require to specify a bias different than default (1.25V).
This adds a property in sgtl5000 codec.
The property is specified in milli-volts so that it is coherent with datasheet.
Signed-off-by: NJean-Michel Hautbois <jean-michel.hautbois@vodalys.com>
Signed-off-by: NMark Brown <broonie@kernel.org>