[XLA:GPU] Remove aggressive while licm from the pipeline.

We used to have to copy constants from host to device before passing them to
black-box conv/matmul routines.  In that setting LICM'ing constant
instructions used to make sense (constants weren't "free").

However, with cr/207204478, constants reside on the device (like normal buffers)
and so we no longer need to H2D copy constants to pass them to black-box
conv/matmul.  Therefore LICM'ing constants is no longer necessary.

PiperOrigin-RevId: 207755572