Refactor and simplify BLAS gemm call further #256

Job	Run time
tests/stable	2m 43s
tests/beta	2m 44s
clippy/stable	25s
tests/nightly	3m 25s
cross_test/s390x-unknown-linux-gnu/stable	5m 29s
tests/1.64.0	3m 51s
cargo-careful	2m 10s
cross_test/i686-unknown-linux-gnu/stable	1m 42s
format/nightly	14s
nostd/thumbv6m-none-eabi/stable	16s
docs/stable	19s
conclusion	1s
	23m 19s

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