usb/hcd: Fix a NULL vs IS_ERR() bug in usb_hcd_setup_local_mem()

The devm_memremap() function doesn't return NULL, it returns error
pointers.

Fixes: b0310c2f ("USB: use genalloc for USB HCs with local memory")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Acked-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://lore.kernel.org/r/20190607135709.GC16718@mwandaSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/core/hcd.c

@@ -3052,8 +3052,8 @@ int usb_hcd_setup_local_mem(struct usb_hcd *hcd, phys_addr_t phys_addr,
 
 	local_mem = devm_memremap(hcd->self.sysdev, phys_addr,
 				  size, MEMREMAP_WC);
-	if (!local_mem)
-		return -ENOMEM;
+	if (IS_ERR(local_mem))
+		return PTR_ERR(local_mem);
 
 	/*
 	 * Here we pass a dma_addr_t but the arg type is a phys_addr_t.