mei: amthif: replace amthif_rd_complete_list with rd_completed

Now when we have per client rd_completed list we can remove
the amthif specific amthif_rd_complete_list.
In addition in the function mei_amthif_read do not loop over the
rd_completed list like the original code as the code path is unlocked.

Reviewed-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>