drivers/wireless/ieee802154/mrf24j40: Fixes minor lockup bug and cleans up some formatting

Approved-by: Gregory Nutt <gnutt@nuttx.org>

stm32f429i-disco, stm3240g-eval, stm3220g-eval, stm3210e-eval:  Eliminate duplicate Make.defs files.

ieee802154: Many small bug fixes clean-ups that help stabilize the functionality

Approved-by: Gregory Nutt <gnutt@nuttx.org>

configs/clicker2-stm32/mrf24j40-mac: Updates stack size to 2048 to avoid random stack overflows when logging is enabled

Build System:  It is no longer necessary to have a unique Make.defs file for each configuration.  A board may share a common Make.defs file in the scripts directory.