drm/amdgpu/gfx10: fix wptr reset in KGQ init

wptr is a 64 bit value and we need to update the
full value, not just 32 bits. Align with what we
already do for KCQs.

Reviewed-by: Timur Kristóf <[e-mail]>
Reviewed-by: Jesse Zhang <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>
(cherry picked from commit e80b1d1aa1073230b6c25a1a72e88f37e425ccda)
Cc: [e-mail]

drivers/gpu/drm/amd/amdgpu/gfx_v10_0.c

···
 			memcpy_toio(mqd, adev->gfx.me.mqd_backup[mqd_idx], sizeof(*mqd));
 		/* reset the ring */
 		ring->wptr = 0;
-		*ring->wptr_cpu_addr = 0;
+		atomic64_set((atomic64_t *)ring->wptr_cpu_addr, 0);
 		amdgpu_ring_clear_ring(ring);
 	}