gpu: nvgpu: increase l2 flush timeout

Under heavy throttling case gpu runs 8 times slower.
This is making l2 flush to timeout, to avoid this increase
timeout to 10msec from 1msec.

Bug 1787261

Change-Id: Ia112ce968c136135ccb9df4a7364073103684403
Signed-off-by: seshendra Gadagottu <sgadagottu@nvidia.com>
Reviewed-on: http://git-master/r/1216559
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Terje Bergstrom <tbergstrom@nvidia.com>

drivers/gpu/nvgpu/gk20a/mm_gk20a.c

@@ -5114,7 +5114,7 @@ void gk20a_mm_l2_flush(struct gk20a *g, bool invalidate)
 {
 	struct mm_gk20a *mm = &g->mm;
 	u32 data;
-	s32 retry = 200;
+	s32 retry = 2000;
 
 	gk20a_dbg_fn("");