[Bazel] Swap stray td_srcs to deps

This is the last instance of td_srcs in MLIR core build files. `deps` is
generally preferred. There are still some cases where `td_srcs` is
useful where creating a td_library would just be another layer of
indirection, so not (yet) dropping it entirely.

Differential Revision: https://reviews.llvm.org/D106716