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>

arch/loongarch/include/asm/uaccess.h

@@ -229,13 +229,13 @@ extern unsigned long __copy_user(void *to, const void *from, __kernel_size_t n);
 static inline unsigned long __must_check
 raw_copy_from_user(void *to, const void __user *from, unsigned long n)
 {
-	return __copy_user(to, from, n);
+	return __copy_user(to, (__force const void *)from, n);
 }
 
 static inline unsigned long __must_check
 raw_copy_to_user(void __user *to, const void *from, unsigned long n)
 {
-	return __copy_user(to, from, n);
+	return __copy_user((__force void *)to, from, n);
 }
 
 #define INLINE_COPY_FROM_USER