[X86][AVX] Only share broadcasts of different widths from the same SDValue of...

[X86][AVX] Only share broadcasts of different widths from the same SDValue of the same SDNode (PR48215)

D57663 allowed us to reuse broadcasts of the same scalar value by extracting low subvectors from the widest type.

Unfortunately we weren't ensuring the broadcasts were from the same SDValue, just the same SDNode - which failed on multiple-value nodes like ISD::SDIVREM

FYI: I intend to request this be merged into the 11.x release branch.

Differential Revision: https://reviews.llvm.org/D91709