Changes

Rename function s/hnbgw_decode_ranap_co/hnbgw_decode_ranap_cn_co/g

This function is only used to decode UL RANAP messages. Mark it as "CN"
like most other related APIs.

Change-Id: Ia4e5a21a9724ebf759b62c13759a776189b09e91

Add function helper hnbgw_decode_ranap_ran_co()

Similar to already existing counterpart hnbgw_decode_ranap_cn_co().
This helps simplifying logic into smaller chunks, and will make both UL
and DL look more similar.

Change-Id: Ifbb058d5340a6cb3a1703415e49c0de04fa6aec1

Move paging logic to its own file

Paging logic contains quite a lot of logic which is really specific to
paging topic and which can be put together and encapsulated easily.

Furthermore, this logic will mostly grow in the future since right now
we only offer minimal paging features by broadcasting to all HNBs.

Finally, this also simplifies hnbgw_cn.c

Change-Id: I402fdcdc261626798904e7ee2eb5db80d30c4c34

Move DL CL RANAP processing logic to its proper layer file

This way we effectively split lower layers (SCCP and below) related to
the link towards CN from the RANAP payload we need to process and
forward.

Change-Id: Icf18fe66d0483165fe487fe850b25830faf90150

Move DL CO RANAP processing to its proper layer file

Change-Id: Ifcb8a23becb57ccad6c9aa4769b6f27d31a71c96

Move UL CO RANAP processing to its proper layer file

Change-Id: I0d16f6c1c303aa1275322f12faf332de8d7c3147