Prevent ghost keys

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Detect and prevent ghost keypresses

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In this diagram, SW00, SW01, and SW10 are closed. SW11 is open. Without diodes, current can flow:

• From C1 through SW01 to R0
• From R0 through SW00 to C0
• From C0 through SW10 to R1

This makes it appear as though R1 and C1 are connected, which would make SW11 be detected as closed.

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When a keypress happens, the EC should check if the keypress connects 2 inputs and 2 rows with 3 switches. Any time this happens, the fourth switch would invalidly register at the same time.