[PATCH v1 0/2] ieee802154: use macros to replace hard-coded channel masks

(Cleanup) It was noticed that in the previous implementation, the channel
masks were hard-coded in the source code. This patch extracts all channel
masks into a header file.

Commits:
 1. include: add macros for ieee 802.15.4 channel masks
 2. net/ieee802154: use channel mask macros replace the hard-coded magic number