ice: Destroy scheduler tree in reset path

The scheduler tree is is always rebuilt during reset. The existing code
adds new scheduler nodes for queues but may not clean up earlier nodes.
This patch removed the old scheduler tree during reset before it is
rebuilt.

Signed-off-by: Henry Tieman <henry.w.tieman@intel.com>
Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@intel.com>
Tested-by: Andrew Bowers <andrewx.bowers@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>