Human activity sensors report the energy burnt by the user.
One of this devices is Freescale's MMA9553L
(http://www.freescale.com/files/sensors/doc/ref_manual/MMA9553LSWRM.pdf)
that computes the number of calories based on weight and step rate.

Introduce a new channel type ENERGY to export these values.
Signed-off-by: NIrina Tirdea <irina.tirdea@intel.com>
Signed-off-by: NJonathan Cameron <jic23@kernel.org>