[AVX512] Add a test to check what happens when a load is referenced by two...

[AVX512] Add a test to check what happens when a load is referenced by two different masked scalar intrinsics with the same op inputs, but different masking node.

We're missing some single use checks in the sse_load_f32/f64 handling that cause us to replicate the load.

llvm-svn: 311300