x86: uaccess: use errret as error value in __put_user_size()

Impact: cleanup

In __put_user_size() macro errret is used for error value.
But if size is 8, errret isn't passed to__put_user_asm_u64().
This behavior is inconsistent.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>