dt-bindings: iio/accel: Drop duplicate adi,adxl345/6 from trivial-devices.yaml

dt-bindings: iio/accel: Drop duplicate adi,adxl345/6 from trivial-devices.yaml

The 'adi,adxl345' definition is a duplicate as there's a full binding in:
Documentation/devicetree/bindings/iio/accel/adi,adxl345.yaml

The trivial-devices binding doesn't capture that 'adi,adxl346' has a
fallback compatible 'adi,adxl345', so let's add it to adi,adxl345.yaml.

Signed-off-by: Rob Herring <robh@kernel.org>
Acked-by: Alexandru Ardelean <alexandru.ardelean@analog.com>
Cc: Peter Meerwald-Stadler <pmeerw@pmeerw.net>
Cc: Michael Hennerich <michael.hennerich@analog.com>
Cc: Hartmut Knaack <knaack.h@gmx.de>
Cc: linux-iio@vger.kernel.org
Cc: Lars-Peter Clausen <lars@metafoo.de>
Cc: Jonathan Cameron <jic23@kernel.org>