f32-spmm missing tests

Currently the way tests are generated and linked causes an issue where in the final binary 'f32-spmm-minmax-test' only the tests present in 'f32-spmm-minmax.cc' get included. I'm building for a RISC-V target but I don't believe target platform affects final output for the test binary.
I've managed to hack my way around this by generating the source code for the code in one file 'f32-spmm-minmax.cc' but this should get fixed properly. Also consider re-evaluating other tests that are split into multiple files.