[Hotfix] Typo in Vulkan runtime change causing severe perf regression for dGPU

[masahi]

I found that #7833 introduced severe perf regression for vk + dGPU. Running cuda_gemm_square.py on R9 nano, I found that vk result is extremely slow:

Device opencl                                                                                                                                       
average time cost of 10 runs = 3.57431 ms, 4806.48 GFLOPS.

Device vulkan                   
average time cost of 10 runs = 39.8278 ms, 431.354 GFLOPS.

After bisecting, I found that I had a typo in #7833 resulting in using a wrong memory type for device buffers 🤦‍♂️ Interestingly, there is no regression for APU, so I didn't notice during development. Now this has been fixed and vk performance is great as before:

Device opencl
average time cost of 10 runs = 3.56969 ms, 4812.7 GFLOPS.

Device vulkan
average time cost of 10 runs = 3.04882 ms, 5634.93 GFLOPS.

cc @tqchen