staging: wilc1000: modified NULL check used for 'if' condition in delete_key()

Fix below issue reported by checkpatch.pl script.

'Comparison to NULL could be written "priv->wilc_gtk[key_index]"'
'Comparison to NULL could be written "priv->wilc_ptk[key_index]"'
Signed-off-by: Ajay Singh <ajay.kathat@microchip.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/wilc1000/wilc_wfi_cfgoperations.c

@@ -1038,7 +1038,7 @@ static int del_key(struct wiphy *wiphy, struct net_device *netdev,
 	wl = vif->wilc;
 
 	if (netdev == wl->vif[0]->ndev) {
-		if (priv->wilc_gtk[key_index] != NULL) {
+		if (priv->wilc_gtk[key_index]) {
 			kfree(priv->wilc_gtk[key_index]->key);
 			priv->wilc_gtk[key_index]->key = NULL;
 			kfree(priv->wilc_gtk[key_index]->seq);
@@ -1048,7 +1048,7 @@ static int del_key(struct wiphy *wiphy, struct net_device *netdev,
 			priv->wilc_gtk[key_index] = NULL;
 		}
 
-		if (priv->wilc_ptk[key_index] != NULL) {
+		if (priv->wilc_ptk[key_index]) {
 			kfree(priv->wilc_ptk[key_index]->key);
 			priv->wilc_ptk[key_index]->key = NULL;
 			kfree(priv->wilc_ptk[key_index]->seq);