[CUBLAS] Set fp32 compute and scale dtypes in fp16 matmul

[ibsidorenko]

This commit replaces fp16 compute dtype and scale dtype by fp32 in cublas matmul.

According to cuBLAS docs there are two possible options for compute/scale dtype when input/output dtype is fp16:

1. compute dtype is fp16 and scale dtype is fp16
2. compute dtype is fp32 and scale dtype is fp32

By default, we use 1) in apache/tvm and 2) in octoml/tvm. This commit aligns different behaviour and set fp32 as default.

cc @vinx13 @masahi