[mac] enable wake-up frame periodic sniffing #16

Job	Run time
packet-verification-1-1-on-1-4	12m 17s
thread-1-4-gcc-m32	8m 18s
thread-1-4-gcc-m64	8m 10s
thread-1-4-clang-10-m32	1m 11s
thread-1-4-clang-10-m64	1m 12s
channel-manager-csl	3m 30s
expects	8m 55s
packet-verification-low-power	10m 21s
thread-1-4-posix	10m 0s
upload-coverage	0s
	1h 3m 54s

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