nir_to_tgsi: Remove the abs on fcsel's bool src.
While the nir fcsel opcode specifies src0 != 0.0, as the comment says, it's only ever used on bools-as-floats, so we know that src0 is non-negative. This saves an instruction per CMP on i915.
While the nir fcsel opcode specifies src0 != 0.0, as the comment says, it's only ever used on bools-as-floats, so we know that src0 is non-negative. This saves an instruction per CMP on i915.