[mlir][gpu] Add dump-ptx option

When targeting NVIDIA GPUs, seeing the generated PTX is important. Currently, we don't have simple way to do it.

This work adds dump-ptx to gpu-to-cubin pass. One can use it like `gpu-to-cubin{chip=sm_90 features=+ptx80 dump-ptx}`.

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D155166