iree: VMLA timing out running dynamic-shape PRelu

Describe the bug The keras layers test using the VMLA backend times out, even with a 15 minute timeout. The math here is not complex enough to warrant that. I’ve reproduced the behavior using the input IR with just IREE core.

To Reproduce Steps to reproduce the behavior: Compile and run this IR on the VMLA backend: https://gist.github.com/GMNGeoffrey/60d9f7bc68eeaaf9f576ec6109ed5f35

$ iree-translate prelu.mlir --iree-hal-target-backends=vmla -iree-mlir-to-vm-bytecode-module -o prelu.vmfb
$ iree-run-module prelu.vmfb --entry_function=PReLU__3x3x3x3x3__f32__uniform --function_inputs=3x3x3x3x3xf32