staging: r8188eu: replace rtw_netdev_priv define with inline function

The function guarantees type checking of arguments and return value.

Result of rtw_netdev_priv macro can be assigned to pointer
with incompatible type without warning. The function allow compiler
to perform this check.

Signed-off-by: Ivan Safonov <insafonov@gmail.com>
Link: https://lore.kernel.org/r/20200801180235.34116-1-insafonov@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/rtl8188eu/include/osdep_service.h

@@ -71,8 +71,11 @@ struct rtw_netdev_priv_indicator {
 };
 struct net_device *rtw_alloc_etherdev_with_old_priv(void *old_priv);
 
-#define rtw_netdev_priv(netdev)					\
-	(((struct rtw_netdev_priv_indicator *)netdev_priv(netdev))->priv)
+static inline struct adapter *rtw_netdev_priv(struct net_device *netdev)
+{
+	return ((struct rtw_netdev_priv_indicator *)netdev_priv(netdev))->priv;
+}
+
 void rtw_free_netdev(struct net_device *netdev);
 
 #define FUNC_NDEV_FMT "%s(%s)"