ath10k: deinit copy engine before resetting

Since copy engine allocation has been revised the
ath10k_pci_ce_deinit() now simply zeroes copy
engine registers. It's probably a good idea to do
that before reseting for a more graceful device
reset.

Before ath10k_pci_ce_deinit() freed copy engine
ringbuffer memory so it was required to call it
after resetting. Otherwise it was possible for
device to access unmapped/freed copy engine
ringbuffer memory.

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