selftests/bpf: verifier/value_or_null.c converted to inline assembly

Test verifier/value_or_null.c automatically converted to use inline assembly.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20230325025524.144043-40-eddyz87@gmail.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>