powerpc: set CONFIG_PPC_OF=y always for ARCH=powerpc

The CONFIG_PPC_OF symbol is used to mean that the firmware device tree
access functions are available.  Since we always have a device tree
with ARCH=powerpc, make CONFIG_PPC_OF always Y for ARCH=powerpc.

This fixes some compile errors reported by Kumar Gala, but in a
different way to his patch.  This also makes prom_parse.o be compiled
only if CONFIG_PPC_OF so that non-OF ARCH=ppc platforms will compile.
Signed-off-by: Paul Mackerras <paulus@samba.org>

arch/powerpc/Kconfig

@@ -329,9 +329,7 @@ config PPC_CELL
 	select MMIO_NVRAM
 
 config PPC_OF
-	bool
-	depends on PPC_MULTIPLATFORM	# for now
-	default y
+	def_bool y
 
 config XICS
 	depends on PPC_PSERIES
@@ -399,7 +397,6 @@ config IBMVIO
 config IBMEBUS
 	depends on PPC_PSERIES
 	bool "Support for GX bus based adapters"
-	default y
 	help
 	  Bus device driver for GX bus based adapters.
 

arch/powerpc/kernel/Makefile

@@ -12,8 +12,7 @@ CFLAGS_btext.o		+= -fPIC
 endif
 
 obj-y				:= semaphore.o cputable.o ptrace.o syscalls.o \
-				   irq.o align.o signal_32.o pmc.o vdso.o \
-				   prom_parse.o
+				   irq.o align.o signal_32.o pmc.o vdso.o
 obj-y				+= vdso32/
 obj-$(CONFIG_PPC64)		+= setup_64.o binfmt_elf32.o sys_ppc32.o \
 				   signal_64.o ptrace32.o systbl.o \
@@ -22,7 +21,7 @@ obj-$(CONFIG_PPC64)		+= setup_64.o binfmt_elf32.o sys_ppc32.o \
 obj-$(CONFIG_PPC64)		+= vdso64/
 obj-$(CONFIG_ALTIVEC)		+= vecemu.o vector.o
 obj-$(CONFIG_POWER4)		+= idle_power4.o
-obj-$(CONFIG_PPC_OF)		+= of_device.o
+obj-$(CONFIG_PPC_OF)		+= of_device.o prom_parse.o
 procfs-$(CONFIG_PPC64)		:= proc_ppc64.o
 obj-$(CONFIG_PROC_FS)		+= $(procfs-y)
 rtaspci-$(CONFIG_PPC64)		:= rtas_pci.o

arch/powerpc/kernel/head_32.S

@@ -120,10 +120,12 @@ __start:
  * because OF may have I/O devices mapped into that area
  * (particularly on CHRP).
  */
+#ifdef CONFIG_PPC_MULTIPLATFORM
 	cmpwi	0,r5,0
 	beq	1f
 	bl	prom_init
 	trap
+#endif
 
 /*
  * Check for BootX signature when supporting PowerMac and branch to