ath10k: enable Atheros 802.11ac driver

ath10k: enable Atheros 802.11ac driver

This enables usage of the ath10k driver on OpenWrt. Only 2.0 PCI hardware
is supported. The ath10k firmware is currently only available
through github so use that as its source for now.

This goes build tested, not run time tested.

[Hauke: I did some minor changes]

Cc: ath10k@lists.infradead.org
Cc: Kalle Valo <kvalo@qca.qualcomm.com>
Cc: Kathy Giori <kgiori@qca.qualcomm.com>
Cc: Mathieu Olivari <mathieu@qca.qualcomm.com>
Cc: Jerome Proffit <jproffit@qca.qualcomm.com>
Cc: Sujith Manoharan <c_manoha@qca.qualcomm.com>
Cc: Matthew McClintock <mmcclint@qca.qualcomm.com>
Signed-off-by: Luis R. Rodriguez <mcgrof@qca.qualcomm.com>
Signed-off-by: Hauke Mehrtens <hauke@hauke-m.de>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@37898 3c298f89-4303-0410-b956-a3cf2f4a3e73