lr-wpan: Status enumeration fixes

The status enumeration used in confirm and indication MAC primitives is broken into multiple enumerations (1 per each primitive). This is a problem when connecting higher layers, it is prone to errors and difficult to maintain.

This patch unifies all the MAC primitive status enumerations into a single enumeration. This is consistent with hardware implementations of the standard.

For reference see Table 76 in IEEE 802.15.4-2006

LrWpanAssociationStatus enumeration also needs to be integrated, but this will be addressed in the following patch.

Edit: It was easier to add this in this MR, therefore I included it in the present MR.

RELEASE_NOTES and CHANGES will be added before the merge.