staging: wilc1000: remove pointer varialbes of hif_cs

Remove hif_lock and hif_critical_section which are pointer of
g_linux_wlan->hif_cs. Remove also it's related codes.
Just use mutex varialbe g_linux_wlan->hif_cs.

Signed-off-by: Glen Lee <glen.lee@atmel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>