Fix the following coccicheck warning:

drivers/net/wireless/broadcom/b43/phy_n.c:5510:19-32: WARNING:
Comparison of 0/1 to bool variable

Signed-off-by: Jason Yan <yanaijie@huawei.com>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Link: https://lore.kernel.org/r/20200504113300.40895-1-yanaijie@huawei.com