mfd: Convert 88pm860x to use regmap api

Convert the 88pm860x normal bank register read/write to
use the register map API.

Signed-off-by: Jett.Zhou <jtzhou@marvell.com>
Reviewed-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index f1391c2..c9acd32 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -12,6 +12,7 @@
 config MFD_88PM860X
 	bool "Support Marvell 88PM8606/88PM8607"
 	depends on I2C=y && GENERIC_HARDIRQS
+	select REGMAP_I2C
 	select MFD_CORE
 	help
 	  This supports for Marvell 88PM8606/88PM8607 Power Management IC.