nir/opt_peephole_select: Don't peephole_select expensive math instructions

On some GPUs, especially older Intel GPUs, some math instructions are
very expensive.  On those architectures, don't reduce flow control to a
csel if one of the branches contains one of these expensive math
instructions.

This prevents a bunch of cycle count regressions on pre-Gen6 platforms
with a later patch (intel/compiler: More peephole select for pre-Gen6).

v2: Remove stray #if block.  Noticed by Thomas.

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Thomas Helland <thomashelland90@gmail.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>

src/compiler/nir/nir.h

@@ -3198,7 +3198,7 @@ bool nir_opt_move_comparisons(nir_shader *shader);
 bool nir_opt_move_load_ubo(nir_shader *shader);
 
 bool nir_opt_peephole_select(nir_shader *shader, unsigned limit,
-                             bool indirect_load_ok);
+                             bool indirect_load_ok, bool expensive_alu_ok);
 
 bool nir_opt_remove_phis_impl(nir_function_impl *impl);
 bool nir_opt_remove_phis(nir_shader *shader);