mfd: wm5110: Set FX_CTRL2 to volatile

FX_CTRL2 is a volatile register and should be marked as such, this patch
does so.
Signed-off-by: NCharles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: NLee Jones <lee.jones@linaro.org>

drivers/mfd/wm5110-tables.c

@@ -2349,6 +2349,7 @@ static bool wm5110_volatile_register(struct device *dev, unsigned int reg)
 	case ARIZONA_IRQ_PIN_STATUS:
 	case ARIZONA_AOD_IRQ1:
 	case ARIZONA_AOD_IRQ2:
+	case ARIZONA_FX_CTRL2:
 	case ARIZONA_ASRC_STATUS:
 	case ARIZONA_DSP_STATUS:
 	case ARIZONA_DSP1_CONTROL_1: