staging: most: allocate only all requested memory

This prohibits the allocation of the memory for the MBOs if only the
part of the MBOs, requested by the application, may be allocated.  The
function arm_mbo_chain, if cannot allocate all requested MBO, frees all
prior allocated memory and returns 0.

Signed-off-by: Andrey Shvetsov <andrey.shvetsov@k2l.de>
Signed-off-by: Christian Gromm <christian.gromm@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>