i965: drop dead #include "config.h"

There hasn't been a config.h in a long time (it was an artifact of the
autotool build).

Signed-off-by: Eric Engestrom <eric@engestrom.ch>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Dylan Baker <dylan@pnwbakers.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5350>

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

@@ -31,10 +31,6 @@
  *          Dave Airlie <airlied@linux.ie>
  */
 
-#ifdef HAVE_CONFIG_H
-#include "config.h"
-#endif
-
 #include <xf86drm.h>
 #include <util/u_atomic.h>
 #include <fcntl.h>