dix: attach unbound screens to protocol screen 0 (v2)

This is the default attachment, unbound gpu screens get
attached to the 0 protocol screen.

detach on hotunplug.

v2: detach after tearing down crtc/outputs.

Reviewed-by: Keith Packard <keithp@keithp.com>
Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

hw/xfree86/common/xf86Init.c

@@ -920,6 +920,9 @@ InitOutput(ScreenInfo * pScreenInfo, int argc, char **argv)
 #endif
     }
 
+    for (i = 0; i < xf86NumGPUScreens; i++)
+        AttachUnboundGPU(xf86Screens[0]->pScreen, xf86GPUScreens[i]->pScreen);
+
     xf86VGAarbiterWrapFunctions();
     OsReleaseSIGIO();
 

hw/xfree86/modes/xf86Crtc.c

@@ -736,6 +736,11 @@ xf86CrtcCloseScreen(ScreenPtr screen)
 
         crtc->randr_crtc = NULL;
     }
+    /* detach any providers */
+    if (config->randr_provider) {
+        if (screen->current_master)
+            DetachUnboundGPU(screen);
+    }
     xf86RandR12CloseScreen(screen);
 
     free(config->name);