staging: wilc1000: wilc_wlan.c: use BIT(x) macro

Remove bit shift macro that is custom defined, then replace BIT(x)
macro.

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>