mm: Make arch_unmap()/bprm_mm_init() available to all architectures

mm: Make arch_unmap()/bprm_mm_init() available to all architectures

The x86 MPX patch set calls arch_unmap() and arch_bprm_mm_init()
from fs/exec.c, so we need at least a stub for them in all
architectures.  They are only called under an #ifdef for
CONFIG_MMU=y, so we can at least restict this to architectures
with MMU support.

blackfin/c6x have no MMU support, so do not call arch_unmap().
They also do not include mm_hooks.h or mmu_context.h at all and
do not need to be touched.

s390, um and unicore32 do not use asm-generic/mm_hooks.h, so got
their own arch_unmap() versions.  (I also moved um's
arch_dup_mmap() to be closer to the other mm_hooks.h functions).

xtensa only includes mm_hooks when MMU=y, which should be fine
since arch_unmap() is called only from MMU=y code.

For the rest, we use the stub copies of these functions in
asm-generic/mm_hook.h.

I cross compiled defconfigs for cris (to check NOMMU) and s390
to make sure that this works.  I also checked a 64-bit build
of UML and all my normal x86 builds including PARAVIRT on and
off.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: linux-arch@vger.kernel.org
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/20141118182350.8B4AA2C2@viggo.jf.intel.com
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>