ath10k: Fix target to cpu address conversion logic

In commit 418ca599 ("ath10k: Make target cpu address to
CE address conversion chip specific") mask 0x7fff is added
by mistake instead of 0x7ff. Fix this regression.

Fixes: 418ca599

 ("ath10k: Make target cpu address to CE address conversion chip specific")
Signed-off-by: Vasanthakumar Thiagarajan <vthiagar@qti.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>