[WATCHDOG] Atmel AT91RM9200 rename.

The new Atmel AT91SAM9261 and AT91SAM9260 processors use a different
internal watchdog peripheral.  This watchdog driver is therefore
AT91RM9200-specific.

This patch renames at91_wdt.c to at91rm9200_wdt.c, and changes the name
of the configuration option.

Signed-off-by: Andrew Victor <andrew@sanpeople.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
diff --git a/arch/arm/configs/at91rm9200dk_defconfig b/arch/arm/configs/at91rm9200dk_defconfig
index c82e466..b430414 100644
--- a/arch/arm/configs/at91rm9200dk_defconfig
+++ b/arch/arm/configs/at91rm9200dk_defconfig
@@ -577,7 +577,7 @@
 # Watchdog Device Drivers
 #
 # CONFIG_SOFT_WATCHDOG is not set
-CONFIG_AT91_WATCHDOG=y
+CONFIG_AT91RM9200_WATCHDOG=y
 
 #
 # USB-based Watchdog Cards