It is not necessary to flush tlb page on all CPUs if suitable PTE
entry exists already during page fault handling, just updating
TLB is fine.

Here redefine flush_tlb_fix_spurious_fault as empty on MIPS system.
Signed-off-by: Bibo Mao <maobibo@loongson.cn>
Signed-off-by: Thomas Bogendoerfer <tsbogend@alpha.franken.de>