Revert "powerpc/powernv: hwmon driver for power values, fan rpm and temperature"

This reverts commit 0de7f8a9

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This driver wasn't merged via the proper maintainers (my fault ... ooops !)
and has serious issues so let's take it out for now and have a new better
one be merged the right way

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
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