nir: get ffma support from NIR options for nir_lower_flrp

This also fixes the inverted last parameter of nir_lower_flrp in most drivers.

Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6599>

src/intel/compiler/brw_nir.c

@@ -597,8 +597,7 @@ brw_nir_optimize(nir_shader *nir, const struct brw_compiler *compiler,
       if (lower_flrp != 0) {
          if (OPT(nir_lower_flrp,
                  lower_flrp,
-                 false /* always_precise */,
-                 compiler->devinfo->gen >= 6)) {
+                 false /* always_precise */)) {
             OPT(nir_opt_constant_folding);
          }