drivers: sensor: ccs811: reset sensor when driver is initialized

The CCS811 has a measurement lifecycle that includes certain timing
constraints, including that calibration constants should not be applied
until the conditioning period has completed.  If a device resets but the
CCS811 remains the process of inspecting current state and initializing
the device properly can be complicated.

Simplify this by forcing a reset of the device when the driver is
initialized.  Should this cause hardship the necessary logic and
infrastructure to record time-of-last-reset across reboots and verify
measurement mode/baseline consistency can be added at that point.

Signed-off-by: Peter A. Bigot <pab@pabigot.com>