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

This reverts commit 0de7f8a9.

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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