slirp: Fix spelling in comment (enought -> enough, insure -> ensure)

Signed-off-by: NStefan Weil <sw@weilnetz.de>
Signed-off-by: NStefan Hajnoczi <stefanha@gmail.com>

slirp/ip_icmp.h

@@ -92,8 +92,8 @@ struct icmp {
 
 /*
  * Lower bounds on packet lengths for various types.
- * For the error advice packets must first insure that the
- * packet is large enought to contain the returned ip header.
+ * For the error advice packets must first ensure that the
+ * packet is large enough to contain the returned ip header.
  * Only then can we do the check to see if 64 bits of packet
  * data have been returned, since we need to check the returned
  * ip header length.