ath9k_hw: Handle AR_INTR_SYNC_HOST1_(FATAL|PERR) on AR9003

Interrupts with the sync_cause AR_INTR_SYNC_HOST1_FATAL and
AR_INTR_SYNC_HOST1_PERR have to be handled using a chip reset. Otherwise a
interrupt storm with unhandled interrupts will cause a hang or crash of the
machine.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>