powerpc/mm: get rid of nohash/32/mmu.h and nohash/64/mmu.h

Those files have no real added values, especially the 64 bit
which only includes the common book3e mmu.h which is also
included from 32 bits side.

So lets do the final inclusion directly from nohash/mmu.h

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>