ARM: at91: add Shutdown Controller (SHDWC) DT support

Use a string to specific the wakeup mode to make it more readable.

Add the Real-time Clock Wake-up support too for sam9g45 and sam9x5.
Add AT91_SHDW_CPTWK0_MAX to specific the Max of the Wakeup Counter.

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Acked-by: Nicolas Ferre <nicolas.ferre@atmel.com>
diff --git a/arch/arm/boot/dts/at91sam9g45.dtsi b/arch/arm/boot/dts/at91sam9g45.dtsi
index 587a191..8908f07 100644
--- a/arch/arm/boot/dts/at91sam9g45.dtsi
+++ b/arch/arm/boot/dts/at91sam9g45.dtsi
@@ -83,6 +83,11 @@
 			};
 
 
+			shdwc@fffffd10 {
+				compatible = "atmel,at91sam9rl-shdwc";
+				reg = <0xfffffd10 0x10>;
+			};
+
 			tcb0: timer@fff7c000 {
 				compatible = "atmel,at91rm9200-tcb";
 				reg = <0xfff7c000 0x100>;