ath9k: make some hardware reset log messages debug-only

On some chips, baseband watchdog hangs are more common than others, and
the driver has support for handling them.
Interrupts even after a watchdog hang are also quite common, so there's
not much point in spamming the user's logfiles.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>