iio: imu: inv_icm42600: Add support for icm42631

Add the required WHOAMI and device_id definitions to support the
icm42631.

Signed-off-by: Jay Greco <grecojay@amazon.com>
Acked-by: Jean-Baptiste Maneyrol <jean-baptiste.maneyrol@tdk.com>
Link: https://lore.kernel.org/r/20221110192933.13616-2-grecojay@amazon.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>