ath10k: merge is_protected with nohwcrypt

It was wasteful to have two flags describing
the same thing.

While at it fix code style of
ath10k_tx_h_use_hwcrypto().

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