drm/fb-helper: Fix the dummy remove_conflicting_framebuffers

We always need to remove conflicting framebuffers if any other fb driver
is enabled, and not just if we are setting up an fbdev ourselves.

Unfortunately remove_conflicting_framebuffers() was incorrectly stubbed
out if !fbdev rather than !fb leading to major memory corruption (and
corrupt filesystems) upon boot.

Fixes: 44adece5 ("drm/fb-helper: Add a dummy remove_conflicting_framebuffers")
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: Tobias Jakobi <tjakobi@math.uni-bielefeld.de>
Cc: Noralf Trønnes <noralf@tronnes.org>
Cc: tomi.valkeinen@ti.com
Cc: dh.herrmann@gmail.com
Cc: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/20160822204452.2509-1-chris@chris-wilson.co.uk

include/drm/drm_fb_helper.h

@@ -282,12 +282,6 @@ drm_pick_cmdline_mode(struct drm_fb_helper_connector *fb_helper_conn,
 int drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper, struct drm_connector *connector);
 int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
 				       struct drm_connector *connector);
-static inline int
-drm_fb_helper_remove_conflicting_framebuffers(struct apertures_struct *a,
-					      const char *name, bool primary)
-{
-	return remove_conflicting_framebuffers(a, name, primary);
-}
 #else
 static inline int drm_fb_helper_modinit(void)
 {
@@ -482,11 +476,17 @@ drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
 	return 0;
 }
 
+#endif
+
 static inline int
 drm_fb_helper_remove_conflicting_framebuffers(struct apertures_struct *a,
 					      const char *name, bool primary)
 {
+#if IS_ENABLED(CONFIG_FB)
+	return remove_conflicting_framebuffers(a, name, primary);
+#else
 	return 0;
-}
 #endif
+}
+
 #endif