x86: Cleanly separate use of asm-generic/mm_hooks.h

asm-generic/mm_hooks.h provides some generic fillers for the 90%
of architectures that do not need to hook some mmap-manipulation
functions.  A comment inside says:

> Define generic no-op hooks for arch_dup_mmap and
> arch_exit_mmap, to be included in asm-FOO/mmu_context.h
> for any arch FOO which doesn't need to hook these.

So, does x86 need to hook these?  It depends on CONFIG_PARAVIRT.
We *conditionally* include this generic header if we have
CONFIG_PARAVIRT=n.  That's madness.

With this patch, x86 stops using asm-generic/mmu_hooks.h entirely.
We use our own copies of the functions.  The paravirt code
provides some stubs if it is disabled, and we always call those
stubs in our x86-private versions of arch_exit_mmap() and
arch_dup_mmap().

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dave Hansen <dave@sr71.net>
Cc: x86@kernel.org
Link: http://lkml.kernel.org/r/20141118182349.14567FA5@viggo.jf.intel.com


Signed-off-by: Thomas Gleixner <tglx@linutronix.de>