cfg80211: allow setting station parameters in mesh

Mesh Point interfaces can also set parameters, for example plink_open is
used to manually establish peer links from user-space (currently via
iw).  Add Mesh Point to the check in nl80211_set_station.

Signed-off-by: Andrey Yurovsky <andrey@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>