Add support for firmware controls marked SYSTEM. These are
internal to the driver-firmware interface and do not have
a user-accessible ALSA control.
Signed-off-by: NStuart Henderson <stuarth@opensource.wolfsonmicro.com>
Signed-off-by: NRichard Fitzgerald <rf@opensource.wolfsonmicro.com>
Signed-off-by: NMark Brown <broonie@kernel.org>