[mac] enable wake-up frame periodic sniffing #39

Job	Run time
packet-verification-low-power	10m 27s
thread-1-4-gcc-m32	11m 32s
thread-1-4-gcc-m64	11m 9s
thread-1-4-clang-10-m32	11m 2s
thread-1-4-clang-10-m64	10m 45s
channel-manager-csl	3m 16s
expects	31m 42s
packet-verification-1-1-on-1-4	11m 55s
thread-1-4-posix	10m 13s
upload-coverage	24s
	1h 52m 25s

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