mei: add POWERING_DOWN into device state print

The POWERING_DOWN state string was missing from
the device states list, add it.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Link: https://lore.kernel.org/r/20211223094705.204624-1-tomas.winkler@intel.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>