usercopy: force check_object_size() inline

Just for good measure, make sure that check_object_size() is always
inlined too, as already done for copy_*_user() and __copy_*_user().

Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Kees Cook <keescook@chromium.org>

include/linux/thread_info.h

@@ -118,7 +118,7 @@ static inline int arch_within_stack_frames(const void * const stack,
 extern void __check_object_size(const void *ptr, unsigned long n,
 					bool to_user);
 
-static inline void check_object_size(const void *ptr, unsigned long n,
+static __always_inline void check_object_size(const void *ptr, unsigned long n,
 					      bool to_user)
 {
 	if (!__builtin_constant_p(n))