bpf: fix env->peak_states computation

Compute env->peak_states as a maximum value of sum of
env->explored_states and env->free_list size.

Signed-off-by: Eduard Zingerman <eddyz87@gmail.com>
Link: https://lore.kernel.org/r/20250215110411.3236773-11-eddyz87@gmail.com


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