bpf: extract register state printing

Extract printing register state representation logic into a separate
helper, as we are going to reuse it for spilled register state printing
in the next patch. This also nicely reduces code nestedness.

No functional changes.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20231118034623.3320920-4-andrii@kernel.org


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