[AGPGART] Add missing cache flush to the generic remove routine.

It's not entirely clear whether this is needed, or it was working around
the missing PCI Posting workaround.  Until we know any better, make
the generic routine do what the per chipset routines do.

Spotted-by: Alan Cox
Signed-off-by: Dave Jones <davej@redhat.com>

drivers/char/agp/generic.c

@@ -905,6 +905,7 @@ int agp_generic_remove_memory(struct agp_memory *mem, off_t pg_start, int type)
 		readl(agp_bridge->gatt_table+i);	/* PCI Posting. */
 	}
 
+	global_cache_flush();
 	agp_bridge->driver->tlb_flush(mem);
 	return 0;
 }