MovingAverage3 => MovingSum3

[jackkoenig]

The example in the README is a sum, not an average.

h/t @soronpo and @BracketMaster for discussions on Gitter: https://gitter.im/freechipsproject/chisel3?at=60f4adc0ec10653d5a49fe18, also discussed in dev: #2049

I thought about making it average over 4 cycles and using a right-shift to do a proper divide, but the purpose of the example is leading into the generalized FIR filter that follows so I kept it the same and just renamed it.

Marked 3.4.x so this change is reflected on the website.

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Type of Improvement

• documentation

API Impact

No impact

Backend Code Generation Impact

No impact

Desired Merge Strategy

• Squash

Release Notes

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[jackkoenig]

I'm not sure who originally wrote this example, maybe @grebe or @stevobailey have strong opinions about the name but seems more clear to call it a sum. Will also need a similar change to the bootcamp.

[stevobailey]

Yeah one of us did it for the bootcamp. This one is a sum since the coefficients are all 1. So, nice catch!