staging: wilc1000: wilc_wlan.c: remove hif_func of wilc_wlan_dev_t

hif_func of wilc_wlan_dev_t is duplicate because we have same struct
wilc_hif_func ops of struct wilc which is available in wilc_wlan.c.
Rename ops of struct wilc with hif_func and remove hif_func of wilc_wlan_dev_t,
and use wilc->hif_func instead of g_wlan.hif_func in all functions.

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