mei: keep the device awake during reads in chunks

Long messages are read in chunks, to prevent trashing runtime pm between
the reading of the chunks we call pm_runtime_mark_last_busy() on
non-final chunk message as the next chunk of the same message will be
received immediately in the next interrupt with high probablity.

Signed-off-by: Alexander Usyskin <alexander.usyskin@intel.com>
Signed-off-by: Tomas Winkler <tomas.winkler@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>