f2fs: fix to active page in lru list for read path

If config CONFIG_F2FS_FAULT_INJECTION is on, for both read or write path
we will call find_lock_page() to get the page, but for read path, it
missed to passing FGP_ACCESSED to allocator to active the page in LRU
list, result in being reclaimed in advance incorrectly, fix it.

Reported-by: Xianrong Zhou <zhouxianrong@huawei.com>
Signed-off-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>