LoongArch: Fix copy_thread() build errors
Commit
2b740c6defb09b6f ("fork: Pass struct kernel_clone_args into
copy_thread") change the prototype of copy_thread(), while commit
680b077b8adbf921 ("fork: Generalize PF_IO_WORKER handling") change
the structure of kernel_clone_args. They cause build errors, so fix it.
Fixes: 680b077b8adbf921 ("fork: Generalize PF_IO_WORKER handling")
Fixes: 2b740c6defb09b6f ("fork: Pass struct kernel_clone_args into copy_thread")
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>