at91: introduce commom AT91_BASE_SYS

On all at91 except rm9200 and x40 have the System Controller starts
at address 0xffffc000 and has a size of 16KiB.

On rm9200 it's start at 0xfffe4000 of 111KiB with non reserved data starting
at 0xfffff000

This patch removes the individual definitions of AT91_BASE_SYS and
replaces them with a common version at base 0xfffffc000 and size 16KiB
and map the same memory space

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Cc: Nicolas Ferre <nicolas.ferre@atmel.com>
Cc: Patrice Vilchez <patrice.vilchez@atmel.com>
diff --git a/arch/arm/mach-at91/board-gsia18s.c b/arch/arm/mach-at91/board-gsia18s.c
index 1d4f36b..6588143 100644
--- a/arch/arm/mach-at91/board-gsia18s.c
+++ b/arch/arm/mach-at91/board-gsia18s.c
@@ -577,7 +577,7 @@
 
 MACHINE_START(GSIA18S, "GS_IA18_S")
 	.timer		= &at91sam926x_timer,
-	.map_io		= at91sam9260_map_io,
+	.map_io		= at91_map_io,
 	.init_early	= gsia18s_init_early,
 	.init_irq	= init_irq,
 	.init_machine	= gsia18s_board_init,