Remove screendump dummy functions.

The code in console.c verifies whenever a screen_dump function
pointer is present before calling it, so there is no need to supply an
dummy function.  Remove them.  Also report an error to notify the user
that he didn't got a screenshot.
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

console.c

@@ -184,6 +184,8 @@ void vga_hw_screen_dump(const char *filename)
     console_select(0);
     if (consoles[0] && consoles[0]->hw_screen_dump) {
         consoles[0]->hw_screen_dump(consoles[0]->hw, filename);
+    } else {
+        error_report("screen dump not implemented");
     }
 
     if (previous_active_console) {

hw/jazz_led.c

@@ -205,11 +205,6 @@ static void jazz_led_invalidate_display(void *opaque)
     s->state |= REDRAW_SEGMENTS | REDRAW_BACKGROUND;
 }
 
-static void jazz_led_screen_dump(void *opaque, const char *filename)
-{
-    printf("jazz_led_screen_dump() not implemented\n");
-}
-
 static void jazz_led_text_update(void *opaque, console_ch_t *chardata)
 {
     LedState *s = opaque;
@@ -255,7 +250,7 @@ static int jazz_led_init(SysBusDevice *dev)
 
     s->ds = graphic_console_init(jazz_led_update_display,
                                  jazz_led_invalidate_display,
-                                 jazz_led_screen_dump,
+                                 NULL,
                                  jazz_led_text_update, s);
 
     return 0;

hw/pxa2xx_lcd.c

@@ -899,11 +899,6 @@ static void pxa2xx_invalidate_display(void *opaque)
     s->invalidated = 1;
 }
 
-static void pxa2xx_screen_dump(void *opaque, const char *filename)
-{
-    /* TODO */
-}
-
 static void pxa2xx_lcdc_orientation(void *opaque, int angle)
 {
     PXA2xxLCDState *s = (PXA2xxLCDState *) opaque;
@@ -1009,7 +1004,7 @@ PXA2xxLCDState *pxa2xx_lcdc_init(MemoryRegion *sysmem,
 
     s->ds = graphic_console_init(pxa2xx_update_display,
                                  pxa2xx_invalidate_display,
-                                 pxa2xx_screen_dump, NULL, s);
+                                 NULL, NULL, s);
 
     switch (ds_get_bits_per_pixel(s->ds)) {
     case 0: