There is currently a build failure for x86_32 in mainline due to JDK-8346038 moving things around. The failure looks like this:

```
* For target hotspot_variant-server_libjvm_objs_c1_LinearScan_x86.o:
src/hotspot/cpu/x86/c1_LinearScan_x86.cpp: In member function 'void FpuStackAllocator::handle_op1(LIR_Op1*)':
src/hotspot/cpu/x86/c1_LinearScan_x86.cpp:652:12: error: 'class LIR_Op1' has no member named 'set_fpu_stack_size'
  652 | op1->set_fpu_stack_size(sim()->stack_size());
      | ^~~~~~~~~~~~~~~~~~
```

This does not warrant a fix, given the code is in deprecated x86_32 parts. But we do not need the whole `set_fpu_stack_size` infra to begin with: the last uses were removed by JDK-8143353 and JDK-8152907. So we can clean up this part for both x86_64 and x86_32 at once, and fix an easy build failure meanwhile.