mfd: Export pm80x_regmap_config

This fixes below build error when CONFIG_MFD_88PM800=m.

ERROR: "pm80x_regmap_config" [drivers/mfd/88pm800.ko] undefined!
make[1]: *** [__modpost] Error 1
make: *** [modules] Error 2
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>

drivers/mfd/88pm80x.c

@@ -29,6 +29,7 @@ const struct regmap_config pm80x_regmap_config = {
 	.reg_bits = 8,
 	.val_bits = 8,
 };
+EXPORT_SYMBOL_GPL(pm80x_regmap_config);
 
 int __devinit pm80x_init(struct i2c_client *client,
 				 const struct i2c_device_id *id)