md: remove_and_add_spares() to activate specific rdev
md: remove_and_add_spares() to activate specific rdev

remove_and_add_spares() checks for all devices to activate spare.
Change it to activate a specific device if a non-null rdev
argument is passed.

remove_and_add_spares() can be used to activate spares in
slot_store() as well.

For hot_remove_disk(), check if rdev->raid_disk == -1 before
calling remove_and_add_spares()

Signed-off-by: Goldwyn Rodrigues <c9a1f5b69e66eac203c1a3ccc3e06e47e8b65275@suse.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs