mfd: Separate out STMPE controller and interface specific code

Few STMPE controller can have register interface over SPI or I2C. Current
implementation only supports I2C and all code is present in a single file
stmpe.c. It would be better to separate out I2C interface specific code from
controller specific code. Later SPI specific code can be added in a separate
file.

This patch separates out I2C and controller specific code into separate files,
making stmpe.c independent of I2C.

Signed-off-by: Viresh Kumar <viresh.kumar@st.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Samuel Ortiz <sameo@linux.intel.com>
diff --git a/drivers/mfd/Kconfig b/drivers/mfd/Kconfig
index 08a3e08..7bc5581 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -279,6 +279,17 @@
 		Keypad: stmpe-keypad
 		Touchscreen: stmpe-ts
 
+menu "STMPE Interface Drivers"
+depends on MFD_STMPE
+
+config STMPE_I2C
+	bool "STMPE I2C Inteface"
+	depends on I2C
+	default y
+	help
+	  This is used to enable I2C interface of STMPE
+endmenu
+
 config MFD_TC3589X
 	bool "Support Toshiba TC35892 and variants"
 	depends on I2C=y && GENERIC_HARDIRQS