ath10k: configure copy engine 5 for HTT messages

Currently target to host (T2H) HTT messages are received at copy engine 1.
These messages are processed by HTC layer in both host and target.
To avoid HTC level processing overhead in both host and target,
the unused copy engine 5 is being used for receiving HTT T2H messages.
This will speedup the receive data processing as well as htt tx completion.
Hence host and target copy engine configuration tables are updated
to enable CE5 pipe. The in-direction HTT mapping is now pointing to CE5
for all HTT T2H.

Moreover HTT send completion messages are polled from HTC handler
as CE 4 is not interrupt-driven. For faster tx completion, CE4 polling
needs to be done whenever CE pipe which transports HTT Rx (target->host)
is processed. This avoids overhead of polling HTT messages from HTC
layer. Servicing CE 4 faster is helping to solve "failed to transmit
packet, dropping: -105".

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