MIPS: 64-bit: Fix system lockup.

The address range size calculation inside local_flush_tlb_kernel_range()
is being truncated by a too small size variable holder on 64-bit systems.
The truncated size can result in an erroneous tlbsize check that means we
sit spinning inside a loop trying to flush a hige number of TLB entries.
This is for all intents and purposes a system hang. Fix by using an
appropriately sized valiable to hold the size.

[Ralf: Greg's original patch submission identified the issue and fixed one
instance in tlb-r4k.c but there there were several more.  For consistency
I also modified tlb-r3k.c even though that file is only used on 32-bit.]

Signed-off-by: Greg Ungerer <gerg@snapgear.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>