OMAP2+: voltage: split out voltage processor (VP) code into new layer

This patch is primarily a move of VP specific code from voltage.c into
its own code in vp.c and adds prototypes to vp.h

No functional changes, except debugfs...

VP debugfs moved to 'vp' subdir of <debugfs>/voltage/ and 'vp_'
prefixes removed from all debugfs filenames.

Signed-off-by: Kevin Hilman <khilman@ti.com>

arch/arm/mach-omap2/Makefile

@@ -90,7 +90,7 @@ obj-$(CONFIG_ARCH_OMAP4)		+= prcm.o cm2xxx_3xxx.o cminst44xx.o \
 
 # OMAP voltage domains
 ifeq ($(CONFIG_PM),y)
-voltagedomain-common			:= voltage.o vc.o
+voltagedomain-common			:= voltage.o vc.o vp.o
 obj-$(CONFIG_ARCH_OMAP2)		+= $(voltagedomain-common) \
 					   voltagedomains2xxx_data.o
 obj-$(CONFIG_ARCH_OMAP3)		+= $(voltagedomain-common) \