sys_log: replace old debug macros at ieee802154 driver

ieee802154 driver is now using new system log macros, update the
Kconfig variable to be a level rather than a bool and the .conf
files at samples.

JIRA: ZEP-311

Change-Id: I640e973d880c3a222cd7c13a72d35edf49ada3a8
Signed-off-by: Genaro Saucedo Tejada <genaro.saucedo.tejada@intel.com>