MIPS: Do not flush tlb page when updating PTE entry

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: NBibo Mao <maobibo@loongson.cn>
Signed-off-by: NThomas Bogendoerfer <tsbogend@alpha.franken.de>

arch/mips/include/asm/pgtable.h

@@ -478,6 +478,11 @@ static inline pgprot_t pgprot_writecombine(pgprot_t _prot)
 	return __pgprot(prot);
 }
 
+static inline void flush_tlb_fix_spurious_fault(struct vm_area_struct *vma,
+						unsigned long address)
+{
+}
+
 /*
  * Conversion functions: convert a page and protection to a page entry,
  * and a page entry and page directory to the page they refer to.