AP_InertialSensor: fixed Q calculation for notch filters #40989

Job	Run time
build (base)	4m 38s
build (clang)	4m 10s
autotest (sitltest-rover)	19m 49s
autotest (sitltest-sailboat)	6m 57s
autotest (sitltest-balancebot)	8m 16s
	43m 50s

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