DDF: find_vdcr: fix minor bug in debug message

This code could find disk -1. Fixed.

Signed-off-by: NeilBrown <neilb@suse.de>
DDF: ddf_activate_spare: Add RAID10 code

The check for degraded array is a bit more complex for RAID10.
Fixing it.

Signed-off-by: NeilBrown <neilb@suse.de>
DDF: ddf_activate_spare: only activate good drives

Do not try to activate drives marked missing or failed.

Signed-off-by: NeilBrown <neilb@suse.de>
DDF: ddf_activate_spare: fix metadata update for SVDs

Metadata updates for secondary RAID (RAID10) need to cover
all BVDs. Compare with code in write_init_super_ddf().

Signed-off-by: NeilBrown <neilb@suse.de>