Move ACPI power meter driver to hwmon

As discussed earlier, the ACPI power meter driver would better live
in drivers/hwmon, as its only purpose is to create hwmon-style
interfaces for ACPI 4.0 power meter devices. Users are more likely to
look for it there, and less likely to accidentally hide it by
unselecting its dependencies.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Acked-by: "Darrick J. Wong" <djwong@us.ibm.com>
Acked-by: Guenter Roeck <guenter.roeck@ericsson.com>
Cc: Len Brown <lenb@kernel.org>