net: trickle: Misc changes

* Fix the indentation which was caused by uint32_t -> u8_t changes.
* Make sure there is no unused variable warning if debugging is
  enabled but debug level is low.
* Add assert that checks that Imax_abs is > 0 which it should be.

Signed-off-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
2 files changed