Add debugfs entry for disabling frames buffering that may be a reason
for mt7603 instability. This patch was sent upstream for review and at
least wasn't rejected yet. Let's add it to let OpenWrt users test if it
really helps.
Example usage:
echo N > /sys/kernel/debug/ieee80211/phy0/mt76/frames_buffering
Signed-off-by: Rafał Miłecki <rafal@milecki.pl>