fastboot: Ensure we treat CONFIG_FASTBOOT_BUF_ADDR as long

Otherwise:
drivers/usb/gadget/f_fastboot.c:564:32: warning: format "%lx" expects
argument of type "long unsigned int", but argument 3 has type "unsigned
int" [-Wformat=]

Signed-off-by: Tom Rini <trini@konsulko.com>

drivers/usb/gadget/f_fastboot.c

@@ -561,7 +561,7 @@ static void do_bootm_on_complete(struct usb_ep *ep, struct usb_request *req)
 
 	puts("Booting kernel..\n");
 
-	sprintf(boot_addr_start, "0x%lx", CONFIG_FASTBOOT_BUF_ADDR);
+	sprintf(boot_addr_start, "0x%lx", (long)CONFIG_FASTBOOT_BUF_ADDR);
 	do_bootm(NULL, 0, 2, bootm_args);
 
 	/* This only happens if image is somehow faulty so we start over */