can: mscan-mpc5xxx: fix return value check in mpc512x_can_get_clock()

In case of error, the function clk_get() returns ERR_PTR()
and never returns NULL pointer. The NULL test in the error
handling should be replaced with IS_ERR().

dpatch engine is used to auto generated this patch.
(https://github.com/weiyj/dpatch)

Cc: stable <stable@vger.kernel.org>
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Acked-by: Wolfgang Grandegger <wg@grandegger.com>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Author: Wei Yongjun

drivers/net/can/mscan/mpc5xxx_can.c

@@ -181,7 +181,7 @@ static u32 __devinit mpc512x_can_get_clock(struct platform_device *ofdev,
 
 		if (!clock_name || !strcmp(clock_name, "sys")) {
 			sys_clk = clk_get(&ofdev->dev, "sys_clk");
-			if (!sys_clk) {
+			if (IS_ERR(sys_clk)) {
 				dev_err(&ofdev->dev, "couldn't get sys_clk\n");
 				goto exit_unmap;
 			}
@@ -204,7 +204,7 @@ static u32 __devinit mpc512x_can_get_clock(struct platform_device *ofdev,
 
 		if (clocksrc < 0) {
 			ref_clk = clk_get(&ofdev->dev, "ref_clk");
-			if (!ref_clk) {
+			if (IS_ERR(ref_clk)) {
 				dev_err(&ofdev->dev, "couldn't get ref_clk\n");
 				goto exit_unmap;
 			}