tun: Fixed unsigned/signed comparison
tun: Fixed unsigned/signed comparison

Validated that this was actually using the unsigned comparison with gdb.

Signed-off-by: Alex Gartrell <a001c4cc1f7f4525442b9f89c44a0f93f2479dd5@fb.com>
Signed-off-by: David S. Miller <fe08d3c717adf2ae63592e4c9aec6e3e404d8e3e@davemloft.net>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs