drm/bochs: Delete an unnecessary check before drm_gem_object_unreference_unlocked()

The drm_gem_object_unreference_unlocked() function tests whether
its argument is NULL and then returns immediately.
Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1e3a8c0d-e737-f092-727e-af7e3810b8dc@users.sourceforge.net

drivers/gpu/drm/bochs/bochs_mm.c

@@ -474,8 +474,8 @@ int bochs_dumb_mmap_offset(struct drm_file *file, struct drm_device *dev,
 static void bochs_user_framebuffer_destroy(struct drm_framebuffer *fb)
 {
 	struct bochs_framebuffer *bochs_fb = to_bochs_framebuffer(fb);
-	if (bochs_fb->obj)
-		drm_gem_object_unreference_unlocked(bochs_fb->obj);
+
+	drm_gem_object_unreference_unlocked(bochs_fb->obj);
 	drm_framebuffer_cleanup(fb);
 	kfree(fb);
 }