wil6210: do not set IE's for beacon

On the DMG band, there is no 'normal' beacon frame.
Instead, transmitted is short 'DMG beacon' frame, that do not include IE's
So, beacon IE's are not relevant for the DMG band.

Signed-off-by: Vladimir Kondratiev <qca_vkondrat@qca.qualcomm.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>