security: fix pedantic compilation

security: fix pedantic compilation

/x86_64-native-linuxapp-gcc/include/rte_security.h:229:8:
error: struct has no members [-Werror=pedantic]
  struct rte_security_macsec_xform {
         ^~~~~~~~~~~~~~~~~~~~~~~~~
/x86_64-native-linuxapp-gcc/include/rte_security.h:453:3:
error: struct has no members [-Werror=pedantic]
    struct {
    ^~~~~~

Fixes: c261d1431bd8 ("security: introduce security API and framework")
Cc: stable@dpdk.org
Signed-off-by: Nelio Laranjeiro <nelio.laranjeiro@6wind.com>
Acked-by: Akhil Goyal <akhil.goyal@nxp.com>