Fix unused parameter warning

qnearfieldtarget_neard_p.cpp:52:54: warning: unused parameter `isPersistent` [-Wunused-parameter]
bool QNearFieldTargetPrivate::setKeepConnection(bool isPersistent)

Change-Id: Ib16e986f88452bb043afb973113747f56379ffaf
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@qt.io>

src/nfc/qnearfieldtarget_neard_p.cpp

@@ -51,6 +51,7 @@ bool QNearFieldTargetPrivate::keepConnection() const
 
 bool QNearFieldTargetPrivate::setKeepConnection(bool isPersistent)
 {
+    Q_UNUSED(isPersistent);
     return false;
 }