r600/sfn: Don't put b2f64 conversion into ALU group
There is no need to pin the ops into channels because these are 32 bit ops that can be executed independent from each other. Fixes: 79ca456b r600/sfn: rewrite NIR backend v2: grammar fixes (lorn10) Signed-off-by:Gert Wollny <gert.wollny@collabora.com> Part-of: <mesa/mesa!28840> (cherry picked from commit 2bb102f0)