i965: Silence unused parameter warnings in generated OA code

i965: Silence unused parameter warnings in generated OA code

Reduces my build from 6301 warnings to 2075 warnings by silencing 4226
instances of things like

src/mesa/drivers/dri/i965/i965@sta/brw_oa_hsw.c: In function ‘hsw__render_basic__gpu_core_clocks__read’:
src/mesa/drivers/dri/i965/i965@sta/brw_oa_hsw.c:41:62: warning: unused parameter ‘brw’ [-Wunused-parameter]
 hsw__render_basic__gpu_core_clocks__read(struct brw_context *brw,
                                                              ^~~

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>