usb: gadget: lpc32xx_udc.c: adjust inconsistent IS_ERR and PTR_ERR

Change the call to PTR_ERR to access the value just tested by IS_ERR.

The semantic match that finds this problem is as follows:
(http://coccinelle.lip6.fr/)

// <smpl>
@@
expression e,e1;
@@

(
if (IS_ERR(e)) { ... PTR_ERR(e) ... }
|
if (IS_ERR(e=e1)) { ... PTR_ERR(e) ... }
|
*if (IS_ERR(e))
 { ...
*  PTR_ERR(e1)
   ... }
)
// </smpl>

Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/lpc32xx_udc.c

@@ -3176,7 +3176,7 @@ static int __init lpc32xx_udc_probe(struct platform_device *pdev)
 	udc->usb_otg_clk = clk_get(&pdev->dev, "ck_usb_otg");
 	if (IS_ERR(udc->usb_otg_clk)) {
 		dev_err(udc->dev, "failed to acquire USB otg clock\n");
-		retval = PTR_ERR(udc->usb_slv_clk);
+		retval = PTR_ERR(udc->usb_otg_clk);
 		goto usb_otg_clk_get_fail;
 	}