ARM: at91: Export at91_ramc_base

After commit f363c40 (ARM: at91: make sdram/ddr register base soc independent)
building at91_cf as a module fails with:
  ERROR: "at91_ramc_base" [drivers/pcmcia/at91_cf.ko] undefined!
  make[1]: *** [__modpost] Error 1
  make: *** [modules] Error 2

Export at91_ramc_base symbol to allow drivers using at91_ramc_*
functions to be built as modules again.

Signed-off-by: Joachim Eastwood <joachim.eastwood@jotron.com>
[nicolas.ferre@atmel.com: modify slightly commit message]
Signed-off-by: Nicolas Ferre <nicolas.ferre@atmel.com>

arch/arm/mach-at91/setup.c

@@ -54,6 +54,7 @@ void __init at91_init_interrupts(unsigned int *priority)
 }
 
 void __iomem *at91_ramc_base[2];
+EXPORT_SYMBOL_GPL(at91_ramc_base);
 
 void __init at91_ioremap_ramc(int id, u32 addr, u32 size)
 {