ASoC: msm8916-wcd-digital: Select REGMAP_MMIO to fix build error

Fix below build error:
ERROR: "__devm_regmap_init_mmio_clk" [sound/soc/codecs/snd-soc-msm8916-digital.ko] undefined!

Signed-off-by: Axel Lin <axel.lin@ingics.com>
Acked-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/Kconfig

@@ -706,6 +706,7 @@ config SND_SOC_MSM8916_WCD_ANALOG
 
 config SND_SOC_MSM8916_WCD_DIGITAL
 	tristate "Qualcomm MSM8916 WCD DIGITAL Codec"
+	select REGMAP_MMIO
 
 config SND_SOC_PCM1681
 	tristate "Texas Instruments PCM1681 CODEC"