ab8500_fg: Round capacity output

Round the capacity values for better enduser experience.

Signed-off-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: pender01 <peter.enderborg@stericsson.com>
Reviewed-by: Jonas ABERG <jonas.aberg@stericsson.com>
Tested-by: Marcus COOPER <marcus.xm.cooper@stericsson.com>
Signed-off-by: Anton Vorontsov <anton@enomsg.org>