freedreno/ir3: don't cp absneg into meta:fi

freedreno/ir3: don't cp absneg into meta:fi

If using a fanin (collect) to collect of consecutive registers together,
we can CP mov's into the fanin, but not (abs) or (neg).  No places that
allow those modifiers are consuming a fanin anyways.  But this caused an
absneg to be lost between a ldgb and stgb for shaders like:

  outputs[n] = abs(input[n])

Signed-off-by: Rob Clark <robdclark@gmail.com>