arm64: defconfig: Enable asoc simple mux

This is needed to model the mic input mux on the Librem 5 devkit.
Signed-off-by: Guido Günther <agx@sigxcpu.org>
Signed-off-by: Shawn Guo <shawnguo@kernel.org>

arch/arm64/configs/defconfig

@@ -760,6 +760,7 @@ CONFIG_SND_SOC_GTM601=m
 CONFIG_SND_SOC_PCM3168A_I2C=m
 CONFIG_SND_SOC_RT5659=m
 CONFIG_SND_SOC_SIMPLE_AMPLIFIER=m
+CONFIG_SND_SOC_SIMPLE_MUX=m
 CONFIG_SND_SOC_TAS571X=m
 CONFIG_SND_SOC_WCD934X=m
 CONFIG_SND_SOC_WM8904=m