qt5location: fix build failure due to GCC < 5.x bug in implicit casts

GCC < 5.x has some bug in implicit casts, this leads to build failure.
In particular QPointer<QGeoMap> in m_map QDeclarativeGeoMap class, when
passed to connect(m_map, ...) should directly cast to m_map.data().

Add reworked patch referred on QTBUG-69512:
https://bugreports.qt.io/browse/QTBUG-69512

Fixes:
http://autobuild.buildroot.org/results/dc5/dc5c354f3aae54b77dad74ad44aca6d12425a457/
http://autobuild.buildroot.org/results/3ab/3ab6f79a36543fa677555bc9ec3500baa46ab0f8/
http://autobuild.buildroot.org/results/8b5/8b5531e44c4f4258c950902b2cd92d1ac8a8491e/
http://autobuild.buildroot.org/results/089/089d03ab14a7c70e465cce891506a082049f2998/
http://autobuild.buildroot.org/results/da8/da87ca470b22d599bb25998af8f25136921f35a7/
http://autobuild.buildroot.org/results/5fe/5fe91fd762c5d4eda01378947b13f7ffc084a8be/
http://autobuild.buildroot.org/results/a84/a84182145122935c8f10105818dbf0e3aa23fd11/
http://autobuild.buildroot.org/results/5b9/5b9106351a04646f42697215ed497e09c62c12fa/
http://autobuild.buildroot.org/results/397/397acc3f5d4998a8d632749ef7d21533c35d501a/
http://autobuild.buildroot.org/results/b18/b186ec0e297d6857a9e0a6a063e476b5049ccf93/
http://autobuild.buildroot.org/results/bf2/bf241beeb1ce10eec99d247cdd331870c08e0ac8/



Signed-off-by: Giulio Benetti <giulio.benetti@micronovasrl.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>