md: remove unnecessary code from do_md_run

md: remove unnecessary code from do_md_run

Since commit e6ddce8c0d27101fa12171223a1d51a4bd475b8d,
->hot_remove_disks has not removed non-failed devices from
an array until recovery is no longer possible.
So the code in do_md_run to get around the fact that
md_check_recovery (which calls ->hot_remove_disks) would
remove partially-in-sync devices is no longer needed.

So remove it.

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