ath11k: reset trigger frame MAC padding duration

The value was 3 and it's reserved value. Corrected to maintain fw
defaults.

Signed-off-by: Muna Sinada <msinada@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/1590706483-27609-1-git-send-email-msinada@codeaurora.org