rtl8180: add WMM parameters configuration for rtl8187se

Introduce a new function to configure AC parameters for TX queues
on rtl8187se cards, and hook it onto mac80211 in order to enable
WMM support.

Signed-off-by: Andrea Merello <andrea.merello@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>