b43: nphy.c remove duplicated include

Remove duplicated include <linux/delay.h> in
drivers/net/wireless/b43/nphy.c

Signed-off-by: Huang Weiyi <weiyi.huang@gmail.com>
Signed-off-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: John W. Linville <linville@tuxdriver.com>