ASoC: Support the sub speaker driver on Speyside

Speyside includes a WM9081 configured as an external speaker driver taking
an analogue input from HPOUT2 on the WM8915 on the system. Add support for
this to the driver, using a prefix of "Sub" for the WM9081 controls to
ensure we avoid collisions with controls on the WM8915.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Acked-by: Jassi Brar <jassisinghbrar@gmail.com>
Acked-by: Liam Girdwood <lrg@ti.com>
diff --git a/sound/soc/samsung/Kconfig b/sound/soc/samsung/Kconfig
index 726af2e..459566b 100644
--- a/sound/soc/samsung/Kconfig
+++ b/sound/soc/samsung/Kconfig
@@ -176,3 +176,4 @@
 	depends on SND_SOC_SAMSUNG && MACH_WLF_CRAGG_6410
 	select SND_SAMSUNG_I2S
 	select SND_SOC_WM8915
+	select SND_SOC_WM9081