UPSTREAM: 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>

Change-Id: Ibfdf4790d03fe426e68d9a864c55a0d1bbfb7d61
(cherry picked from commit a85d6b8242dc78ef3f4542a0f979aebcbe77fc4e)
Signed-off-by: Sami Tolvanen <samitolvanen@google.com>