mfd: wm5110: Add missing isolation control register

The isolation control register is required when DCVDD is externally
supplied add this in as a readable register.

Signed-off-by: Charles Keepax <ckeepax@opensource.wolfsonmicro.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

drivers/mfd/wm5110-tables.c

@@ -549,6 +549,7 @@ static const struct reg_default wm5110_reg_default[] = {
 	{ 0x000002A8, 0x1422 },    /* R680   - Mic Detect Level 3 */
 	{ 0x000002A9, 0x300A },    /* R681   - Mic Detect Level 4 */
 	{ 0x000002C3, 0x0000 },    /* R707   - Mic noise mix control 1 */
+	{ 0x000002CB, 0x0000 },    /* R715   - Isolation control */
 	{ 0x000002D3, 0x0000 },    /* R723   - Jack detect analogue */
 	{ 0x00000300, 0x0000 },    /* R768   - Input Enables */
 	{ 0x00000308, 0x0000 },    /* R776   - Input Rate */
@@ -1580,6 +1581,7 @@ static bool wm5110_readable_register(struct device *dev, unsigned int reg)
 	case ARIZONA_MIC_DETECT_LEVEL_3:
 	case ARIZONA_MIC_DETECT_LEVEL_4:
 	case ARIZONA_MIC_NOISE_MIX_CONTROL_1:
+	case ARIZONA_ISOLATION_CONTROL:
 	case ARIZONA_JACK_DETECT_ANALOGUE:
 	case ARIZONA_INPUT_ENABLES:
 	case ARIZONA_INPUT_ENABLES_STATUS: