mfd: max77687: Add registration of max77686-clk

The MAX77686 clock driver has been in-tree for over 6 months, but never
actually enabled through the MFD registration before.

Add it to the table so the device will probe and configure properly.
Signed-off-by: NOlof Johansson <olof@lixom.net>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>

drivers/mfd/max77686.c

@@ -37,6 +37,7 @@
 static struct mfd_cell max77686_devs[] = {
 	{ .name = "max77686-pmic", },
 	{ .name = "max77686-rtc", },
+	{ .name = "max77686-clk", },
 };
 
 static struct regmap_config max77686_regmap_config = {