altos: Record 32-bits for gyro calibration values

The gyro ground calibration values are scaled by 512 to provide a bit
more precision for the computations. This means they don't fit in 16
bits, so change the format of the flight log record. Also change the
reported format so that AltosUI has a chance of figuring it out.

Signed-off-by: Keith Packard <keithp@keithp.com>