drm/amdgpu/vcn: Return void from the stop_dbg_mode

There is no point in returning an int here. It only returns 0 which
the caller never uses. Therefore return void and remove the unnecessary
assignment.

Addresses-Coverity: 1504988 ("Unused value")
Fixes: 8da1170a16e4 ("drm/amdgpu: add VCN4 ip block support")
Reviewed-by: Ruijing Dong <[e-mail]>
Suggested-by: Ruijing Dong <[e-mail]>
Suggested-by: Greg Kroah-Hartman <[e-mail]>
Signed-off-by: Khalid Masum <[e-mail]>
Signed-off-by: Alex Deucher <[e-mail]>

drivers/gpu/drm/amd/amdgpu/vcn_v4_0.c

···
  *
  * Stop VCN block with dpg mode
  */
-static int vcn_v4_0_stop_dpg_mode(struct amdgpu_device *adev, int inst_idx)
+static void vcn_v4_0_stop_dpg_mode(struct amdgpu_device *adev, int inst_idx)
 {
 	uint32_t tmp;
 
···
 	/* disable dynamic power gating mode */
 	WREG32_P(SOC15_REG_OFFSET(VCN, inst_idx, regUVD_POWER_STATUS), 0,
 		~UVD_POWER_STATUS__UVD_PG_MODE_MASK);
-	return 0;
 }
 
 /**
···
 		fw_shared->sq.queue_mode |= FW_QUEUE_DPG_HOLD_OFF;
 
 		if (adev->pg_flags & AMD_PG_SUPPORT_VCN_DPG) {
-			r = vcn_v4_0_stop_dpg_mode(adev, i);
+			vcn_v4_0_stop_dpg_mode(adev, i);
 			continue;
 		}