mcb: Delete num_cells variable which is not required

The num_cells variable is only used in the dev_dbg print,
but we can directly use the ret variable which also includes the same
value.

Signed-off-by: Andreas Werner <andreas.werner@men.de>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>