ath10k: fix HTT op backwards compatibility for QCA6174

Commit 8348db29 ("ath10k: add ATH10K_FW_IE_HTT_OP_VERSION") broke QCA6174
receive side as the HTT ids from ATH10K_FW_HTT_OP_VERSION_MAIN don't have
HTT_TLV_T2H_MSG_TYPE_RX_IN_ORD_PADDR_IND set. Fix this by adding a backwards
compatibility code which sets HTT op version if it's not set by the firmware
image.

Fixes: 8348db29 ("ath10k: add ATH10K_FW_IE_HTT_OP_VERSION")
Reported-by: Michal Kazior <michal.kazior@tieto.com>
Tested-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>