nios2/uaccess: fix sparse errors

virtio wants to read bitwise types from userspace using get_user. At the
moment this triggers sparse errors, since the value is passed through an
integer.

Fix that up using __force.

Suggested-by: Michael S. Tsirkin <[e-mail]>
Signed-off-by: Ley Foon Tan <[e-mail]>

arch/nios2/include/asm/uaccess.h

···
 	const __typeof__(*(ptr)) __user *__gu_ptr = (ptr);		\
 	unsigned long __gu_val;						\
 	__get_user_common(__gu_val, sizeof(*(ptr)), __gu_ptr, __gu_err);\
-	(x) = (__typeof__(x))__gu_val;					\
+	(x) = (__force __typeof__(x))__gu_val;				\
 	__gu_err;							\
 	})
 
···
 	if (access_ok(VERIFY_READ,  __gu_ptr, sizeof(*__gu_ptr)))	\
 		__get_user_common(__gu_val, sizeof(*__gu_ptr),		\
 			__gu_ptr, __gu_err);				\
-	(x) = (__typeof__(x))__gu_val;					\
+	(x) = (__force __typeof__(x))__gu_val;				\
 	__gu_err;							\
 })