[PATCH] rt2x00: get_duration expects values in 100kbs

get_duration expects all speeds to be passed in 100kbs,
this means that passing 2 is incorrect and should be raised to 20

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