i965: Add debug flag to print out the new L3 state during transitions.

Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Kristian Høgsberg  <krh@bitplanet.net>

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

@@ -78,6 +78,7 @@ static const struct debug_control debug_control[] = {
    { "tcs",         DEBUG_TCS },
    { "ds",          DEBUG_TES },
    { "tes",         DEBUG_TES },
+   { "l3",          DEBUG_L3 },
    { NULL,    0 }
 };