This fixes some possible rare issues with the hash code beeing called
with interrupts enabled from update_mmu_cache, and fixes some races in
the iSeries low level htab code by adding an array of spinlocks

This is actually an old patch already present in SLES kernel and that
got "missed" somewhat in the main tree, adapted to recent changes.
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>