Define dummy functions to mdmon.c

Define dummy functions to mdmon.c

Definitions are necessary to compile mdmon.
Metadata specific source code is compiled to mdmon.
Functions used for reshape check pointing:
- restore_stripes()
- save_stripes
- abort_reshape
are not used in mdmon, but they are compiled in it.
To enable mdmon compilation, dummy functions are used.

Signed-off-by: Adam Kwolek <adam.kwolek@intel.com>
Signed-off-by: Krzysztof Wojcik <krzysztof.wojcik@intel.com>
Signed-off-by: NeilBrown <neilb@suse.de>