ath9k: disable the tasklet before taking the PCU lock
ath9k: disable the tasklet before taking the PCU lock

Fixes a reported CPU soft lockup where the tasklet tries to acquire the
lock and blocks while ath_prepare_reset (holding the lock) waits for it
to complete.

Cc: 4fbacc2fa0ffdbb11bf1ad6925b886ebd08dd15f@vger.kernel.org
Reported-by: Robert Shade <f1a08f6d225f38688df8482f300d67157afb7b17@gmail.com>
Signed-off-by: Felix Fietkau <118ed6118e893d16e8c6e0776e0ebc290952c897@openwrt.org>
Signed-off-by: John W. Linville <2a53bac7a5d324865ef46ec4c38b2c0fba1456b4@tuxdriver.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs