cstest: Compare the PPC branch details once and without requiring operands

[phix33]

Your checklist for this pull request

• I've documented or updated the documentation of every API function and struct this PR changes.
• I've added tests that prove my fix is effective or that my feature works (if possible)

Detailed description

A ppc test case that supplies bc: expectations but no operands: passes without comparing anything. tests/details/ppc.yaml already has one (bdnzlrl+): change any of its bc: values to garbage —

             bo: 99            # was 25

and cstest tests/details/ppc.yaml still reports all tests succeeded.

• test_expected_ppc returned early when expected->operands_count == 0, and the whole expected->bc block sat inside the operand loop so branch details were compared once per operand, or not at all for an operand-less case. The block is hoisted out of the loop and the early return replaced with a guard around the operand comparison only.
• The operand loop now iterates expected->operands_count rather than actual->op_count: with the early return gone, the old bound would dereference a NULL expected->operands[i] for an operand-less case.

Test plan

One new case: bdnzflr 4*cr5+eq (4c 16 00 20) with a full bc: block and deliberately no operands:. Any wrong value in it (or in the existing bdnzlrl+ case) passes on unpatched next and fails with this fix.

The other arch comparers don't have this shape: only ppc keeps an instruction-wide block inside its operand loop; the aarch64/arm/sparc/x86 early returns skip operand comparisons only.

Closing issues

None.