set_pte() taking mm and vaddr args

I've modified set_pte() to take 'mm' and 'address' arguments.
This helps sparc64 and ppc platforms a lot in their batched
TLB shootdown implementations.

Before this, those platforms have to figure out the mm
and address at set_pte() time via rogue means.  In the
page_struct of the pte table, they store the 'mm' in
page->mapping, and the base virtual address in page->index

That is just silly, especially since we have all of this
information available at the set_pte() call sites.

I also encourage platforms other than sparc64 and ppc into
using this batched tlb shootdown scheme, it has been found
to be extremely effective.

Could people maintaining other platforms send me the necessary
changes?  For most it's a matter of adding the 'mm' and
'address' args to set_pte() and pte_clear().  If you override
any of the routines in asm-generic/pgtable.h you'll need to update
their args as well.  Finally, if you have set_pte()/pte_clear()
calls in your platform specific code, update those as well.

Thanks a lot to benh for doing the ppc bits for me.

Thanks.