mach-ux500: move the DB8500 PRCMU driver to MFD

We have decided that this function arbiter fits better in the MFD
subsystem. Since we need to concatenate the split header files we move
it basically like this:

mv mach-ux500/prcmu-db8500.c drivers/mfd/db8500-prcmu.c
mv mach-ux500/include/mach/prcmu-defs.h include/linux/mfd/db8500-prcmu.h
mv mach-ux500/include/mach/prcmu-regs.h drivers/mfd/db8500-prcmu-regs.h
mach-ux500/include/mach/prcmu.h >> include/linux/mfd/db8500-prcmu.h
rm arch/arm/mach-ux500/include/mach/prcmu.h

Then we update different #include statements and Makefile orders etc
to make the PRCMU driver compile, link and boot in the new place
without really changing any code.

Acked-by: Samuel Ortiz <sameo@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>