wil6210: Add Tx queue len configuration

Tx queue was hard-coded to 1000 in ether_setup. Add wil_dev_setup
function which configures tx queue len to chosen default value
after calling ether_setup.

Signed-off-by: Vladimir Shulman <qca_shulmanv@qca.qualcomm.com>
Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>