Use a single "+r" constraint instead of the separate "=r" and "0".
Signed-off-by: NIlya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/r/20230128000650.1516334-22-iii@linux.ibm.comSigned-off-by: NAlexei Starovoitov <ast@kernel.org>