powerpc/mm: move platform specific mmu-xxx.h in platform directories

[ Upstream commit 994da93d196866f914c9d64aafb86e95e3decbb2 ]

The purpose of this patch is to move platform specific
mmu-xxx.h files in platform directories like pte-xxx.h files.

In the meantime this patch creates common nohash and
nohash/32 + nohash/64 mmu.h files for future common parts.

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Stable-dep-of: 66b2ca086210 ("powerpc/64s/radix: Fix soft dirty tracking")
Signed-off-by: Sasha Levin <sashal@kernel.org>