staging: wilc1000: use sizeof(*wdev) to allocate memory in wilc_wfi_cfg_alloc()

Fix below reported checkpatch issues in wilc_wfi_cfg_alloc().
kzalloc(sizeof(*wdev)...) over kzalloc(sizeof(struct wireless_dev)

Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>