[plugins/qpa] Adjust to changes in Qt 5.7 QPA interface

BUG: 360269

plugins/qpa/abstractplatformcontext.cpp

@@ -115,10 +115,17 @@ QSurfaceFormat AbstractPlatformContext::format() const
     return m_format;
 }
 
+#if (QT_VERSION < QT_VERSION_CHECK(5, 7, 0))
 QFunctionPointer AbstractPlatformContext::getProcAddress(const QByteArray &procName)
 {
     return eglGetProcAddress(procName.constData());
 }
+#else
+QFunctionPointer AbstractPlatformContext::getProcAddress(const char *procName)
+{
+    return eglGetProcAddress(procName);
+}
+#endif
 
 bool AbstractPlatformContext::isValid() const
 {

plugins/qpa/abstractplatformcontext.h

@@ -39,7 +39,11 @@ public:
     void doneCurrent() override;
     QSurfaceFormat format() const override;
     bool isValid() const override;
+#if (QT_VERSION < QT_VERSION_CHECK(5, 7, 0))
     QFunctionPointer getProcAddress(const QByteArray &procName) override;
+#else
+    QFunctionPointer getProcAddress(const char *procName) override;
+#endif
 
 protected:
     EGLDisplay eglDisplay() const {