6lowpan: iphc: Fix missing blank line after variable declarations

WARNING: Missing a blank line after declarations
+		struct sk_buff *new;
+		if (uncompress_udp_header(skb, &uh))

Signed-off-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: Johan Hedberg <johan.hedberg@intel.com>