staging: most: remove stacked_mbo

This patch makes use of kfifo_peek and kfifo_skip, which renders the
variable stacked_mbo useless. It is therefore removed.

Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>