ath11k: Modify the interrupt timer threshold

Modify the interrupt timer threshold param as 256 to avoid HW watchdog
in heavy multicast traffic scenario.

Signed-off-by: Karthikeyan Periyasamy <periyasa@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1586343957-21474-1-git-send-email-periyasa@codeaurora.org