powerpc: kill PPC_OF

We have set CONFIG_PPC_OF to always 'y' in commit 0a498d96a3
("powerpc: set CONFIG_PPC_OF=y always for ARCH=powerpc") nine years
ago. And the arch/ppc also has gone away for many years. The OF
functionality was also moved to a common place and be used by many
archs. So it does make no sense to keep such a option in the current
kernel. Just kill it.

Signed-off-by: Kevin Hao <haokexin@gmail.com>
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/Makefile

@@ -33,7 +33,8 @@ obj-y				:= cputable.o ptrace.o syscalls.o \
 				   signal.o sysfs.o cacheinfo.o time.o \
 				   prom.o traps.o setup-common.o \
 				   udbg.o misc.o io.o dma.o \
-				   misc_$(CONFIG_WORD_SIZE).o vdso32/
+				   misc_$(CONFIG_WORD_SIZE).o vdso32/ \
+				   of_platform.o prom_parse.o
 obj-$(CONFIG_PPC64)		+= setup_64.o sys_ppc32.o \
 				   signal_64.o ptrace32.o \
 				   paca.o nvram_64.o firmware.o
@@ -47,7 +48,6 @@ obj-$(CONFIG_PPC64)		+= vdso64/
 obj-$(CONFIG_ALTIVEC)		+= vecemu.o
 obj-$(CONFIG_PPC_970_NAP)	+= idle_power4.o
 obj-$(CONFIG_PPC_P7_NAP)	+= idle_power7.o
-obj-$(CONFIG_PPC_OF)		+= of_platform.o prom_parse.o
 procfs-y			:= proc_powerpc.o
 obj-$(CONFIG_PROC_FS)		+= $(procfs-y)
 rtaspci-$(CONFIG_PPC64)-$(CONFIG_PCI)	:= rtas_pci.o