LoongArch: Requires __force attributes for any casts

LoongArch: Requires __force attributes for any casts

This fix a warning when "make C=2":
arch/loongarch/kernel/ptrace.c: note: in included file (through include/linux/uaccess.h, include/linux/sched/task.h, include/linux/sched/signal.h, include/linux/ptrace.h, include/linux/audit.h):
./arch/loongarch/include/asm/uaccess.h:232:32: warning: incorrect type in argument 2 (different address spaces)
./arch/loongarch/include/asm/uaccess.h:232:32:    expected void const *from
./arch/loongarch/include/asm/uaccess.h:232:32:    got void const [noderef] __user *from

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Qing Zhang <zhangqing@loongson.cn>
Signed-off-by: Huacai Chen <chenhuacai@loongson.cn>