ath9k_hw: revert chainmask to user configuration after calibration

The commit 'ath9k_hw: fix calibration issues on chainmask that don't
include chain 0' changed the hardware chainmask to the chip chainmask
for the duration of the calibration, but the revert to user
configuration in the reset path runs too early.

That causes some issues with limiting the number of antennas (including
spurious failure in hardware-generated packets).

Fix this by reverting the chainmask after the essential parts of the
calibration that need the workaround, and before NF calibration is run.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Reported-by: Wojciech Dubowik <Wojciech.Dubowik@neratec.com>
Tested-by: Wojciech Dubowik <Wojciech.Dubowik@neratec.com>
Cc: stable@vger.kernel.org
Signed-off-by: John W. Linville <linville@tuxdriver.com>