powerpc: make iSeries boot again

On ARCH=ppc64 we were getting htab_hash_mask recalculated
to the correct value for our particular machine by accident.
In the merge tree, that code was commented out, so htab_hash_mask
was being corrupted.

We now set ppc64_pft_size instead which gets htab_has_mask
calculated correctly for us later.  We should put an
ibm,pft-size property in the device tree at some point.

Also set -mno-minimal-toc in some makefiles.
Allow iSeries to configure PROC_DEVICETREE.

Signed-off-by: Stephen Rothwell <sfr@canb.auug.org.au>

arch/powerpc/mm/Makefile

@@ -2,6 +2,10 @@
 # Makefile for the linux ppc-specific parts of the memory manager.
 #
 
+ifeq ($(CONFIG_PPC64),y)
+EXTRA_CFLAGS	+= -mno-minimal-toc
+endif
+
 obj-y				:= fault.o mem.o lmb.o
 obj-$(CONFIG_PPC32)		+= init_32.o pgtable_32.o mmu_context_32.o \
 				   tlb_32.o