Moving Average Filter (4 samples)

Moving-average filter over the last 4 samples. A new average is produced on each rising clock edge.

Behaviour:

• Reset (i_reset='1'): all internal registers and o_data are cleared.
• Rising edge of i_clk: i_data is pushed into the delay line, the oldest sample is dropped.
• o_data ← (sum of the 4 stored samples) / 4.

*Division by 4 = right shift by 2 bits. Asynchronous active-high reset.*