mfd: Move the mc13xxx-core spi specific code into a separate module

All spi specific code is moved into a new module. The mc13xxx struct
moves to a new local include file by necessity.

A new config choice selects the SPI bus type support and by default is
value of SPI_MASTER to remain compatible with existing configs.

Signed-off-by: Marc Reilly <marc@cpdesign.com.au>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 411a61a..9c8294c 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -600,14 +600,23 @@
 	depends on SPI_MASTER
 	select MFD_CORE
 	select MFD_MC13783
-	select REGMAP_SPI
 	help
-	  Support for the Freescale (Atlas) PMIC and audio CODECs
-	  MC13783 and MC13892.
-	  This driver provides common support for accessing  the device,
+	  Enable support for the Freescale MC13783 and MC13892 PMICs.
+	  This driver provides common support for accessing the device,
 	  additional drivers must be enabled in order to use the
 	  functionality of the device.
 
+if MFD_MC13XXX
+
+config MFD_MC13XXX_SPI
+	tristate "MC13xxx SPI interface" if SPI_MASTER
+	default SPI_MASTER
+	select REGMAP_SPI
+	help
+	  Select this if your MC13xxx is connected via an SPI bus.
+
+endif
+
 config ABX500_CORE
 	bool "ST-Ericsson ABX500 Mixed Signal Circuit register functions"
 	default y if ARCH_U300 || ARCH_U8500