[qca-nss-ecm] Merge database structures' directional fields.

Instead of using from/to/from_nat/to_nat fields,
use an array with a size of 4.
Change the related places in the code.

Change-Id: I18bee7af125817b8380439d03183af71d1bd5363
Signed-off-by: Murat Sezgin <msezgin@codeaurora.org>
31 files changed