Changed gear data type from Uint8 to Int8
Changed gear data type from Uint8 to Int8

The previous data type was incorrect because a negative value of
-1 means the reverse gear.

Signed-off-by: Rudolf J Streif <3a3f8ba70589896d7aa2a0a0d3bcf865c0bd58b4@jaguarlandrover.com>

GENIVI/vehicle_signal_specification,GENIVI/vehicle_signal_specification