In preparation for the addition of SPI support for the WM831x move the I2C
specific code into a separate file with a separate Kconfig option so the
I2C support can be excluded from the build.

Also update the 1133-EV1 PMIC module support for SMDK6410 to use the new
symbol.
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: NSamuel Ortiz <sameo@linux.intel.com>