nand-part: Add mbr parsing diagnostics.

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Signed-off-by: Henrik Nordstrom <henrik@henriknordstrom.net>
nand-part: Reject wrong partition version.

Signed-off-by: Michal Suchanek <hramrach@gmail.com>
Signed-off-by: Henrik Nordstrom <henrik@henriknordstrom.net>