powerpc: Build kernel with -mcmodel=medium

Finally remove the two level TOC and build with -mcmodel=medium.

Unfortunately we can't build modules with -mcmodel=medium due to
the tricks the kernel module loader plays with percpu data:

# -mcmodel=medium breaks modules because it uses 32bit offsets from
# the TOC pointer to create pointers where possible. Pointers into the
# percpu data area are created by this method.
#
# The kernel module loader relocates the percpu data section from the
# original location (starting with 0xd...) to somewhere in the base
# kernel percpu data space (starting with 0xc...). We need a full
# 64bit relocation for this to work, hence -mcmodel=large.

On older kernels we fall back to the two level TOC (-mminimal-toc)

Signed-off-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/mm/Makefile

@@ -4,7 +4,7 @@
 
 subdir-ccflags-$(CONFIG_PPC_WERROR) := -Werror
 
-ccflags-$(CONFIG_PPC64)	:= -mno-minimal-toc
+ccflags-$(CONFIG_PPC64)	:= $(NO_MINIMAL_TOC)
 
 obj-y				:= fault.o mem.o pgtable.o gup.o \
 				   init_$(CONFIG_WORD_SIZE).o \