ath10k: replace warning with an error message if HTT op version is unset

Print an ath10k error message rather a call trace when HTT op version is
not found from firmware META data (IE). This should be sufficient to figure
out what went wrong.

Signed-off-by: Mohammed Shafi Shajakhan <mohammed@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>