board: MCR3000: use new DM watchdog

This patch switches MCR3000 board to the new DM watchdog.

The change in u-boot.lds is because MCR3000.o grows a bit
with this patch and doesn't fit anymore below env_offset on
some versions of GCC.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
diff --git a/arch/powerpc/dts/mcr3000.dts b/arch/powerpc/dts/mcr3000.dts
index e4b2228..ef423d7 100644
--- a/arch/powerpc/dts/mcr3000.dts
+++ b/arch/powerpc/dts/mcr3000.dts
@@ -9,4 +9,7 @@
 /dts-v1/;
 
 / {
+	WDT: watchdog@0 {
+		compatible = "fsl,pq1-wdt";
+	};
 };