ASoC: Allow SND_SOC_WM8978 to be selected manually

When using a DT-based multi-platform kernel, there's not always Kconfig
logic that selects the right codec driver.
Allow the user to manually select WM8978.

This is needed for Armadillo 800 EVA using a generic r8a7740 multi-platform
kernel.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@linaro.org>

sound/soc/codecs/Kconfig

@@ -712,7 +712,8 @@ config SND_SOC_WM8974
 	tristate
 
 config SND_SOC_WM8978
-	tristate
+	tristate "Wolfson Microelectronics WM8978 codec"
+	depends on I2C
 
 config SND_SOC_WM8983
 	tristate