The flight code assumes corrections have the same sign as the sensor bias error and are subtracted from the raw reading

since the correction topic now contains data from all sensors, we don't
need additional fields in voted_sensors_update

This is needed so that temperature compensation reads in the updated values
and publishes the updated sensor_correction topic.

This is not needed, as s is an uORB instance and accel_offset_0
contains data from uORB instance 0.

this was actually never published, only _0, _1, ... get published

Makes sure that the offsets & scales are updated and published later on.

if compensation enabled, scale & offsets for the drivers should be reset,
but actually only the params were reset and accel_scale was still applied
to the driver via ioctl.

if it's not published yet or published with low frequency, this makes sure
we have valid data.

also:
- _sensor_correction -> sensor_correction
- remove unnecessary init of sensor_correction_sub

This mapping is required so other applications can use the correct compensation data, even if the uORB ordering changes.

The use of a float to integer cast was causing high frequency reporting when the float value was close to the rounding boundary.

Squashed commits:
[f81a8b0] mc_att_control: remove unnecessary initialisers
[f3d3f48] mc_att_control: accommodate changes to sensor_correction topic

Squashed commits:
[2df1d9e] sensors: change definition of sensor offset and scale factor to match legacy code
[089e103] sensors: publish thermal corrections for all sensors

Fixes the following case: a board that has several bus_options enabled,
and wants to start a specific device (eg mpu6000 -T 20608 start). In that
case the given device_type is never actually checked, and since the start
routine iterates over all bus_options, several can match, and thus start
multiple instances of the driver (note that the whoami check is performed
against the value provided with -T and thus the check will pass).

This happens on Pixracer (PX4_SPIDEV_MPU and PX4_SPIDEV_ICM_20608 are both
set).

This is what's used according to https://pixhawk.org/modules/pixracer.

It uses a shared I2C bus with MS65611 which causes noise on the baro
reads. This will rely on the external compass instead of the internal
one.