mfd: Break out ab5500 debugfs code

This breaks the debugfs portions of the AB5500 driver into its own
file. Split off a _raw function to access registers since we don't
want to expose a generically named function globally. Move all
required data structures to a shared ab5500-core.h file.

Cc: Mattias Wallin <mattias.wallin@stericsson.com>
Signed-off-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 8594de8..f22bd2f 100644
--- a/drivers/mfd/Kconfig
+++ b/drivers/mfd/Kconfig
@@ -572,6 +572,14 @@
 	  chip. This connects to the db5500 chip via the I2C bus via PRCMU.
 	  This chip embeds various other multimedia funtionalities as well.
 
+config AB5500_DEBUG
+	bool "Enable debug info via debugfs"
+	depends on AB5500_CORE && DEBUG_FS
+	default y if DEBUG_FS
+	help
+	  Select this option if you want debug information from the AB5500
+	  using the debug filesystem, debugfs.
+
 config AB8500_CORE
 	bool "ST-Ericsson AB8500 Mixed Signal Power Management chip"
 	depends on GENERIC_HARDIRQS && ABX500_CORE