qt5: change upstream URL

The Qt5 upstream URL has changed, which leads to build failures in the
autobuilders.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>

package/qt5/qt5.mk

@@ -1,5 +1,5 @@
 QT5_VERSION = 5.0.2
-QT5_SITE = http://releases.qt-project.org/qt5/$(QT5_VERSION)/submodules/
+QT5_SITE = http://download.qt-project.org/archive/qt/5.0/$(QT5_VERSION)/submodules/
 include package/qt5/*/*.mk
 
 define QT5_LA_PRL_FILES_FIXUP