[TASK] Clean up section macros for Nios II MN

- Remove obsolete section macros
- Add sections to circbuffer
- Add sections to DLLk process functions
- Add section to target function global interrupt enable

Change-Id: Ia1dab1f1c59d57d4d90d5e46817af295d92f901e
[FIX] Clean up circbuf size allocation

This fix cleans up the circbuf header initialization. The aligned size is
forwarded as a pointer to the target dependent function.

Change-Id: I6e8b6023dca440ef7de84be26d1f77849a619756
[TASK] Optimize PDOk channel access

This commit avoids searching for the PDO channel by using a look-up-table
which is addressed with the node ID and returns the PDO channel ID.
The optimization improves processing of many PDO channels.

Change-Id: Ifc2817d2d4c8d29918355a121669d58d6969d727