ath: regd: add extra US coutry codes

This patch adds several country codes to the regd.h and regd_common.h
files in order to support devices like the Linksys EA6350v3, whose
country codes are not present in the original list. Without this patch,
all devices whose manufacturer programmed any of these code in their
EEPROM will not work.

The values for CTRY_UNITED_STATES2 and CTRY_UNITED_STATES3 were taken
from a post by Sven Eckelmann <sven.eckelmann@openmesh.com>:
<http://lists.infradead.org/pipermail/ath10k/2017-August/010014.html>

Signed-off-by: Oever Gonzalez <notengobattery@gmail.com>
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>