usb: musb: dsps: fix devm_ioremap_resource error detection code

devm_ioremap_resource returns an ERR_PTR value, not NULL, on failure.
Furthermore, the value returned by devm_ioremap_resource should be tested.

A simplified version of the semantic match that finds this problem is as
follows: (http://coccinelle.lip6.fr/)

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

*e = devm_ioremap_resource(...);
if (!e1) S

// </smpl>
Signed-off-by: NJulia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/usb/musb/musb_dsps.c

@@ -361,8 +361,8 @@ static int dsps_musb_init(struct musb *musb)
 		return -EINVAL;
 
 	reg_base = devm_ioremap_resource(dev, r);
-	if (!musb->ctrl_base)
-		return -EINVAL;
+	if (IS_ERR(reg_base))
+		return PTR_ERR(reg_base);
 	musb->ctrl_base = reg_base;
 
 	/* NOP driver needs change if supporting dual instance */