vc4: Switch to using a separate ioctl for making shaders.

vc4: Switch to using a separate ioctl for making shaders.

This gives the kernel a chance to validate and lock down the data,
without having to deal with mmap zapping.

With this, GLBenchmark stops on a texture relocations, because we'd
recycled a shader BO as another shader and failed to revalidate, since we
weren't clearing the cached validation state on mmap faults.