ath10k: change ce ring cleanup logic

Make ath10k_pci_init_pipes() effectively only
alter shared target-host data.

The per_transfer_context is a host-only thing.
It is necessary to preserve it's contents for a
more robust ring cleanup.

This is required for future warm reset fixes.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>