ath9k: revert do-not-access-hw-on-IRQ-reset

Fix for https://dev.openwrt.org/ticket/18483
http://net.t-labs.tu-berlin.de/~thomas/999-revert_ath9k_do-not-access-hw-on-IRQ-reset.patch

Fixes b/20588723

Change-Id: Ic33f7b87daca90dc60619c5064242bce23c505cf
1 file changed