Switching channel happens after specific SHM write to B43_SHM_SH_CHAN.
This is the way we found it in BCM4331 MMIO dumps. By comparing with
N-PHY code we noticed there is routing used for SYN and TX/RX.
Signed-off-by: NRafał Miłecki <zajec5@gmail.com>
Signed-off-by: NJohn W. Linville <linville@tuxdriver.com>