ath10k: add support for Ubiquiti rebranded QCA988X v2

Some modern Ubiquiti devices contain a rebranded QCA988X rev2 with
a custom Ubiquiti vendor and device id. This patch adds support for
those devices, treating them as a QCA988X v2.

Signed-off-by: Tobias Schramm <tobleminer@gmail.com>
[kvalo@codeaurora.org: rebase, add missing fields in hw_params, fix a long line in pci.c:61]
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>