aarch64: Avoid redundant MOVs in AdvSIMD F32 logs

Since the last operation is destructive, the first argument to the FMA
also has to be the first argument to the special-case in order to
avoid unnecessary MOVs. Reorder arguments and adjust special-case
bounds to facilitate this.

Reviewed-by: Wilco Dijkstra <Wilco.Dijkstra@arm.com>