hwmon: Remove amd_energy driver

Commit 60268b0e ("hwmon: (amd_energy) modify the visibility of
the counters") restricted visibility of AMD energy counters to work
around a side-channel attack using energy data to determine which
instructions are executed. The attack is described in 'PLATYPUS:
Software-based Power Side-Channel Attacks on x86'. It relies on quick
and accurate energy readings.

This change made the counters provided by the amd_energy driver
effectively unusable for non-provileged users. However, unprivileged
read access is the whole point of hardware monitoring attributes.

An attempt to remedy the situation by limiting and randomizing access
to chip registers was rejected by AMD. Since the driver is for all
practical purposes unusable, remove it.

Cc: Naveen Krishna Chatradhi <nchatrad@amd.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>