wifi: wilc1000: simplify wilc_scan()

Simplify 'wilc_scan()' assuming 'struct wilc_priv *' is the only data
passed to '(*scan_result)()' callback and thus avoid typeless 'void *'
pointers in related code, including 'struct wilc_user_scan_req'.
Compile tested only.

Signed-off-by: Dmitry Antipov <dmantipov@yandex.ru>
Signed-off-by: Kalle Valo <kvalo@kernel.org>
Link: https://lore.kernel.org/r/20231031171330.70399-2-dmantipov@yandex.ru