net: ethernet: ti: cpts: fix unbalanced clk api usage in cpts_register/unregister

There are two issues with TI CPTS code which are reproducible when TI
CPSW ethX device passes few up/down iterations:
- cpts refclk prepare counter continuously incremented after each
up/down iteration;
- devm_clk_get(dev, "cpts") is called many times.

Hence, fix these issues by using clk_disable_unprepare() in
cpts_clk_release() and skipping devm_clk_get() if cpts refclk has been
acquired already.
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/ti/cpts.c

@@ -230,18 +230,20 @@ static void cpts_overflow_check(struct work_struct *work)
 
 static void cpts_clk_init(struct device *dev, struct cpts *cpts)
 {
+	if (!cpts->refclk) {
 		cpts->refclk = devm_clk_get(dev, "cpts");
 		if (IS_ERR(cpts->refclk)) {
 			dev_err(dev, "Failed to get cpts refclk\n");
 			cpts->refclk = NULL;
 			return;
 		}
+	}
 	clk_prepare_enable(cpts->refclk);
 }
 
 static void cpts_clk_release(struct cpts *cpts)
 {
-	clk_disable(cpts->refclk);
+	clk_disable_unprepare(cpts->refclk);
 }
 
 static int cpts_match(struct sk_buff *skb, unsigned int ptp_class,