selftests/bpf: verify states_equal() maintains idmap across all frames

A test case that would erroneously pass verification if
verifier.c:states_equal() maintains separate register ID mappings for
call frames.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20221209135733.28851-5-eddyz87@gmail.com


Signed-off-by: Alexei Starovoitov <ast@kernel.org>