f2fs: set the correct place of initializing *res_page

The function 'find_in_inline_dir()' contain 'res_page'
as an argument. So, we should initiaize 'res_page' before
this function.

Signed-off-by: Yuan Zhong <yuan.mark.zhong@samsung.com>
Reviewed-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>