intel/blorp: Don't use ffma directly

It isn't supported prior to gen6 and, on gen6+, NIR will fuse the fmul
and fadd into an ffma automatically for us anyway.

Reviewed-by: Topi Pohjolainen <topi.pohjolainen@intel.com>

src/intel/blorp/blorp_blit.c

@@ -135,7 +135,7 @@ blorp_blit_apply_transform(nir_builder *b, nir_ssa_def *src_pos,
    nir_ssa_def *mul = nir_vec2(b, nir_channel(b, coord_transform, 0),
                                   nir_channel(b, coord_transform, 2));
 
-   return nir_ffma(b, src_pos, mul, offset);
+   return nir_fadd(b, nir_fmul(b, src_pos, mul), offset);
 }
 
 static inline void