When running heavy traffic we stop the tx queue if the pending
packet count reaches certain threshold. Later, the tx queue should
be woken up as soon as the packet count falls below the threshold.

Current code wakes TX queue up on STA interface only. Removing the
check for STA interface will allow both STA and AP interfaces to
resume transmit when tx_pending count becomes low.
Signed-off-by: Avinash Patil <patila@marvell.com>
Signed-off-by: Bing Zhao <bzhao@marvell.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>