calipso: fix resource leak on calipso_genopt failure

Currently, if calipso_genopt fails then the error exit path
does not free the ipv6_opt_hdr new causing a memory leak. Fix
this by kfree'ing new on the error exit path.

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>