ieee802154: 6lowpan: remove unnecessary comparison

The type of dispatch is u8 which is always '<=' 0xff, so the
dispatch <= 0xff is always true, we can remove this comparison.

Reported-by: Hulk Robot <[e-mail]>
Signed-off-by: Yang Yingliang <[e-mail]>
Signed-off-by: Stefan Schmidt <[e-mail]>
Signed-off-by: Jakub Kicinski <[e-mail]>

net/ieee802154/6lowpan/rx.c

···
 	return ((dispatch >= 0x44 && dispatch <= 0x4F) ||
 		(dispatch >= 0x51 && dispatch <= 0x5F) ||
 		(dispatch >= 0xc8 && dispatch <= 0xdf) ||
-		(dispatch >= 0xe8 && dispatch <= 0xff));
+		dispatch >= 0xe8);
 }
 
 /* lowpan_rx_h_check checks on generic 6LoWPAN requirements