selftests/bpf: Adjust verifier_map_ptr for the map's excl field

selftests/bpf: Adjust verifier_map_ptr for the map's excl field

Adding the u32 excl field at offset 32 of struct bpf_map right after the
sha[SHA256_DIGEST_SIZE] hash shifts the ops pointer from offset 32 to 40.
Therefore, fix up the test case.

  # LDLIBS=-static PKG_CONFIG='pkg-config --static' ./vmtest.sh -- ./test_progs -t verifier_map_ptr
  [...]
  #637/1   verifier_map_ptr/bpf_map_ptr: read with negative offset rejected:OK
  #637/2   verifier_map_ptr/bpf_map_ptr: read with negative offset rejected @unpriv:OK
  #637/3   verifier_map_ptr/bpf_map_ptr: write rejected:OK
  #637/4   verifier_map_ptr/bpf_map_ptr: write rejected @unpriv:OK
  #637/5   verifier_map_ptr/bpf_map_ptr: read non-existent field rejected:OK
  #637/6   verifier_map_ptr/bpf_map_ptr: read non-existent field rejected @unpriv:OK
  #637/7   verifier_map_ptr/bpf_map_ptr: read ops field accepted:OK
  #637/8   verifier_map_ptr/bpf_map_ptr: read ops field accepted @unpriv:OK
  [...]
  Summary: 2/18 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: KP Singh <kpsingh@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20260601150248.394863-7-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>