drm: Don't call virtual methods from a parent class destructor

We'd be relying on AbstractEglDrmBackend on calling cleanup but we'd be
doing it when cleanupSurfaces cannot be reached out anymore, turning it
into a half-baked cleanup.

Instead call cleanup from the leaf class destructors.

src/plugins/platforms/drm/abstract_egl_drm_backend.cpp

@@ -24,11 +24,6 @@ AbstractEglDrmBackend::AbstractEglDrmBackend(DrmBackend *drmBackend, DrmGpu *gpu
     connect(m_gpu, &DrmGpu::outputDisabled, this, &AbstractEglDrmBackend::removeOutput);
 }
 
-AbstractEglDrmBackend::~AbstractEglDrmBackend()
-{
-    cleanup();
-}
-
 void AbstractEglDrmBackend::screenGeometryChanged(const QSize &size)
 {
     Q_UNUSED(size)

src/plugins/platforms/drm/abstract_egl_drm_backend.h

@@ -22,8 +22,6 @@ class DrmOutput;
 class AbstractEglDrmBackend : public AbstractEglBackend
 {
 public:
-    ~AbstractEglDrmBackend();
-
     void screenGeometryChanged(const QSize &size) override;
 
     virtual int screenCount() const = 0;

src/plugins/platforms/drm/egl_gbm_backend.cpp

@@ -41,6 +41,11 @@ EglGbmBackend::EglGbmBackend(DrmBackend *drmBackend, DrmGpu *gpu)
 {
 }
 
+EglGbmBackend::~EglGbmBackend()
+{
+    cleanup();
+}
+
 void EglGbmBackend::cleanupSurfaces()
 {
     for (auto it = m_outputs.begin(); it != m_outputs.end(); ++it) {

src/plugins/platforms/drm/egl_gbm_backend.h

@@ -38,6 +38,7 @@ class EglGbmBackend : public AbstractEglDrmBackend
     Q_OBJECT
 public:
     EglGbmBackend(DrmBackend *drmBackend, DrmGpu *gpu);
+    ~EglGbmBackend() override;
 
     SceneOpenGLTexturePrivate *createBackendTexture(SceneOpenGLTexture *texture) override;
     QRegion beginFrame(int screenId) override;

src/plugins/platforms/drm/egl_stream_backend.cpp

@@ -75,6 +75,11 @@ EglStreamBackend::EglStreamBackend(DrmBackend *drmBackend, DrmGpu *gpu)
 {
 }
 
+EglStreamBackend::~EglStreamBackend()
+{
+    cleanup();
+}
+
 void EglStreamBackend::cleanupSurfaces()
 {
     for (auto it = m_outputs.constBegin(); it != m_outputs.constEnd(); ++it) {

src/plugins/platforms/drm/egl_stream_backend.h

@@ -27,6 +27,7 @@ class EglStreamBackend : public AbstractEglDrmBackend
     Q_OBJECT
 public:
     EglStreamBackend(DrmBackend *b, DrmGpu *gpu);
+    ~EglStreamBackend() override;
     SceneOpenGLTexturePrivate *createBackendTexture(SceneOpenGLTexture *texture) override;
     QRegion beginFrame(int screenId) override;
     void endFrame(int screenId, const QRegion &damage, const QRegion &damagedRegion) override;