agp: Use u32 __iomem annotation to silence sparse warning.

Replace "void *" by "u32 __iomem *" to silence sparse warning.
Signed-off-by: Santosh Nayak <santoshprasadnayak@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

drivers/char/agp/generic.c

@@ -958,7 +958,7 @@ int agp_generic_create_gatt_table(struct agp_bridge_data *bridge)
 	if (set_memory_uc((unsigned long)table, 1 << page_order))
 		printk(KERN_WARNING "Could not set GATT table memory to UC!\n");
 
-	bridge->gatt_table = (void *)table;
+	bridge->gatt_table = (u32 __iomem *)table;
 #else
 	bridge->gatt_table = ioremap_nocache(virt_to_phys(table),
 					(PAGE_SIZE * (1 << page_order)));