Add the register definition CH_BUSY_STA_SEC for reading the busy time
on the secondary channel in HT40 mode. Also update the comments about
channel busy/idle time registers to express the used unit.
Signed-off-by: NHelmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: NIvo van Doorn <IvDoorn@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>