Modify hardware to give buffer board reset control over IMU

[ajn96]

On Rev A/B of the buffer board, the hardware reset pin only goes to the IMU. This makes it so there is no way to force a hardware reset on the buffer board itself.

A more flexible solution would be to wire the reset output from the master device to the reset input on the buffer board. Then, the IMU reset output can be driven from a GPIO on the buffer board (with a pull up). This gives the flexibility for the buffer board to reset the IMU on demand (via command register bit), and also allows users to reset the buffer board firmware, without power cycle or SPI port access required.

[ajn96]

Will use PA3 for IMU reset control

[ajn96]

This has been incorporated into the rev C board design