rt2x00: Fix beacon updates in rt61pci

Fix rt61pci beacon updates in the same way as rt2800pci. rt61pci didn't
update the beacon template after each beacon interval, resulting in the
DTIM count being incorrect (if DTIM period > 1). Fix this by calling
rt2x00lib_beacondone after the current beacon was sent out.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: Ivo van Doorn <IvDoorn@gmail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>