usb: amd5536udc: Fix the type of ep_string

Use "static const char *const" instead of "static const char *".
Signed-off-by: Cyril Roelandt <tipecaml@gmail.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/gadget/amd5536udc.c

@@ -140,7 +140,7 @@ static DECLARE_TASKLET(disconnect_tasklet, udc_tasklet_disconnect,
 
 /* endpoint names used for print */
 static const char ep0_string[] = "ep0in";
-static const char *ep_string[] = {
+static const char *const ep_string[] = {
 	ep0_string,
 	"ep1in-int", "ep2in-bulk", "ep3in-bulk", "ep4in-bulk", "ep5in-bulk",
 	"ep6in-bulk", "ep7in-bulk", "ep8in-bulk", "ep9in-bulk", "ep10in-bulk",