[OLK-6.6] arch/mm/fault: accelerate pagefault when badaccess

“异常”内存访问，比如写只读的内存等，会释放vma锁，重新持有mmap lock大锁，引起性能劣化，但“异常”访问场景无需再次持锁，只需要直接返回上报信号；
因此，跳过再次持锁；

对于lmbench prot_fault 测试用例，可以获得34%的性能提升：
lat_sig -P 1 prot lat_sig 0.29194 -> 0.19198

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