latency_analysis: Add comment to clarify code
latency_analysis: Add comment to clarify code

I didn't understand this line of code, hopefully this comment will help next
time I read it.

bjackman/lisa,arnoldlu/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,credp/lisa,ARM-software/lisa,credp/lisa,credp/lisa,mdigiorgio/lisa,mdigiorgio/lisa,ARM-software/lisa,bjackman/lisa,arnoldlu/lisa