ARM: Remove DISCONTIGMEM support

Everything should now be using sparsemem rather than discontigmem, so
remove the code supporting discontigmem from ARM.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
diff --git a/arch/arm/mm/mm.h b/arch/arm/mm/mm.h
index 815d08e..7b19c90 100644
--- a/arch/arm/mm/mm.h
+++ b/arch/arm/mm/mm.h
@@ -28,7 +28,5 @@
 
 #endif
 
-struct pglist_data;
-
 void __init bootmem_init(void);
-void reserve_node_zero(struct pglist_data *pgdat);
+void reserve_special_regions(void);