Docs: clarify QLowEnergyAdvertisingData::setRawData() limitations

It is only available on Linux Kernel API backend, so explicitly mention
it in the docs. Also explain, why it cannot be supported on other
backends with the current API.

As the new Linux D-Bus backend, together with the Linux Specific docs
section, was introduced only in 6.5, pick this patch down to that
branch only.

Task-number: QTBUG-130146
Task-number: QTBUG-130891
Pick-to: 6.5
Change-Id: I5395fed6606d84ed1d1f032c45b31759330293dd
Reviewed-by: Juha Vuolle <juha.vuolle@qt.io>
(cherry picked from commit 8b95d7779b)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

src/bluetooth/qlowenergyadvertisingdata.cpp

@@ -212,8 +212,9 @@ QList<QBluetoothUuid> QLowEnergyAdvertisingData::services() const
   \note If \a data is longer than 31 bytes, it will be truncated. It is the caller's responsibility
         to ensure that \a data is well-formed.
 
-  Providing the raw advertising data is not supported on BlueZ DBus backend as BlueZ does not
-  support it. This may change in a future release.
+  Setting raw advertising data is only supported on the \l {Linux Specific}
+  {Linux Bluetooth Kernel API} backend. Other backends do not allow to specify
+  the raw advertising data as a global field.
  */
 void QLowEnergyAdvertisingData::setRawData(const QByteArray &data)
 {