security: add reserved bit fields

security: add reserved bit fields

In struct rte_security_ipsec_sa_options, for every new option
added, there is an ABI breakage, to avoid, a reserved_opts
bitfield is added to for the remaining bits available in the
structure.
Now for every new sa option, these reserved_opts can be reduced
and new option can be added.

Signed-off-by: Akhil Goyal <gakhil@marvell.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
Acked-by: Ray Kinsella <mdr@ashroe.eu>