i965: Silence unused parameter warning

All dd functions take a gl_context as the first parameter.  Instead of
removing it, just silence the warning.

brw_performance_monitor.c: In function 'brw_new_perf_monitor':
brw_performance_monitor.c:1354:41: warning: unused parameter 'ctx' [-Wunused-parameter]
 brw_new_perf_monitor(struct gl_context *ctx)
                                         ^

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Carl Worth <cworth@cworth.org>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>

src/mesa/drivers/dri/i965/brw_performance_monitor.c

@@ -1353,6 +1353,7 @@ brw_get_perf_monitor_result(struct gl_context *ctx,
 static struct gl_perf_monitor_object *
 brw_new_perf_monitor(struct gl_context *ctx)
 {
+   (void) ctx;
    return calloc(1, sizeof(struct brw_perf_monitor_object));
 }