ath: add support for special 0x8000 regulatory domain

Two users of ar9170 devices have now reported their cards
have been programmed with a regulatory domain of 0x8000.
This is not a valid regulatory domain as such these users were
unable to use these devices. Since this doesn't seem to be
a device EEPROM corruption we must treat it specially. It
may have been possible the manufacturer intended to use 0x0
as the regulatory domain and that would ultimately yield
to US but since we cannot get confirmationf or this we
default this special case to one of our world regulatory
domains, specifically 0x64.

Reported-by: DavidFreeman on #linux-wireless
Reported-by: Joerg Albert <jal2@gmx.de>
Cc: Christian Lamparter <chunkeey@web.de>,
Cc: Stephen Chen <stephen.chen@atheros.com>
Cc: David Quan <david.quan@atheros.com>
Cc: Tony Yang <tony.yang@atheros.com>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>