gpu: nvgpu: don't skip setting same clk in arbiter

In the current setting, clock arbiter skips setting
the clock if its already set previously. The value
set by the arbiter is stored in
"struct nvgpu_clk_arb->actual" whenever the clock is
updated via the arbiter. However, DVFS might also
update the clock and the updates are not synchronized
with the arbiter. Hence, ensure that any clock
requests are always updated i.e. the requested rate is
set even if the previous rate remains the same.

In the devfreq scale() part, scale emc when clk_arb
is active and skip setting of clocks.

Bug 3666615

Signed-off-by: Debarshi Dutta <ddutta@nvidia.com>
Change-Id: I32bf4dbf81b19fdd6fa0bdec3a6c9a9312b78eca
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nvgpu/+/2727787
Reviewed-by: svcacv <svcacv@nvidia.com>
Reviewed-by: Vijayakumar Subbu <vsubbu@nvidia.com>
GVS: Gerrit_Virtual_Submit <buildbot_gerritrpt@nvidia.com>

drivers/gpu/nvgpu/os/linux/driver_common.c

@@ -100,6 +100,9 @@ static void nvgpu_init_vars(struct gk20a *g)
 	/* Init the clock req count to 0 */
 	nvgpu_atomic_set(&g->clk_arb_global_nr, 0);
 
+	/* Atomic set doesn't guarantee a barrier */
+	nvgpu_smp_wmb();
+
 	nvgpu_mutex_init(&l->ctrl_privs_lock);
 	nvgpu_init_list_node(&l->ctrl_privs);