ath10k: fix incorrect wlan_mac_base in qca6174_regs

In the 'commit ebee76f7 ("ath10k: allow setting coverage class")',
it inherits the design and the address offset from ath9k, but the address
is not applicable to QCA6174, which leads to a random crash while doing the
resume() operation, since the set_coverage_class.ops will be called from
ieee80211_reconfig() when resume() (if the wow is not configured).

Fix the incorrect address offset here to avoid the random crash.

Verified on QCA6174/hw3.0 with firmware WLAN.RM.4.4-00022-QCARMSWPZ-2.

kvalo: this also seems to fix a regression with firmware restart.

Fixes: ebee76f7 ("ath10k: allow setting coverage class")
Cc: <stable@vger.kernel.org> # v4.10
Signed-off-by: Ryan Hsu <ryanhsu@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@qca.qualcomm.com>