ASoC: wm8978: Adjust clock indices so that simple card works

Using simple-card with the wm8978 doesn't work because simple card calls
set_sysclk on the clock index 0, which is not the MCLK in the WM8978.

Adjust the clock definition so that the clock 0 is the MCLK.
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

sound/soc/codecs/wm8978.h

@@ -78,8 +78,8 @@ enum wm8978_clk_id {
 };
 
 enum wm8978_sysclk_src {
+	WM8978_MCLK = 0,
 	WM8978_PLL,
-	WM8978_MCLK
 };
 
 #endif	/* __WM8978_H__ */