thermal: armada: Allow to specify an 'inverted readout' sensor

In order to support inverted-formula thermal sensor readout, this commit
introduces an 'inverted' field in the SoC-specific structure which
allows to specify an inversion of the temperature formula.

Acked-by: Jason Cooper <jason@lakedaemon.net>
Signed-off-by: Ezequiel Garcia <ezequiel.garcia@free-electrons.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>