ar71xx: Unify ath10k calibration data loading

Currently one board uses the "proper" way of providing firmware
with the name ath10k/cal-pci-<pci address>.bin, whereas other
boards patch board.bin template in preinit and rely on a custom
ath10k patch to use calibration data from the template.

This patch makes all boards use the first method.

Signed-off-by: Matti Laakso <malaakso@elisanet.fi>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@46244 3c298f89-4303-0410-b956-a3cf2f4a3e73