ieee802154: atusb: fix firmware version check to enable frame retries

Geert reported: as fw_ver_maj is unsigned char, gcc 4.1.2 complains:

warning: comparison is always true due to limited range of data type

Besides the warning the old check would also fail for firmware versions
like 1.x with x < 3. These would support frame retries, but the driver
would not enable the feature.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Stefan Schmidt <stefan@osg.samsung.com>

drivers/net/ieee802154/atusb.c

@@ -1060,7 +1060,7 @@ static int atusb_probe(struct usb_interface *interface,
 	atusb_get_and_show_build(atusb);
 	atusb_set_extended_addr(atusb);
 
-	if (atusb->fw_ver_maj >= 0 && atusb->fw_ver_min >= 3)
+	if ((atusb->fw_ver_maj == 0 && atusb->fw_ver_min >= 3) || atusb->fw_ver_maj > 0)
 		hw->flags |= IEEE802154_HW_FRAME_RETRIES;
 
 	ret = atusb_get_and_clear_error(atusb);