[MLIR][TOSA] Drop "OnTensors" suffix

This is the only lowering to Linalg Tosa has, so it's needlessly
verbose. Likely this was a carry over from IREE's usage where we
originally lowered to linalg on buffers (the only linalg that existed at
the time), so the everything on tensors needed the suffix. We're dropping
it in IREE also, having transitioned entirely to using Linalg on
tensors.

Reviewed By: sjarus

Differential Revision: https://reviews.llvm.org/D111911