AVR32: Use avr32-linux- cross-compilation prefix by default

It doesn't really matter which toolchain you use to compile u-boot,
but the avr32-linux one is probably what most people have installed.

Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
diff --git a/Makefile b/Makefile
index 84b49fe..a668d45 100644
--- a/Makefile
+++ b/Makefile
@@ -149,7 +149,7 @@
 CROSS_COMPILE = bfin-uclinux-
 endif
 ifeq ($(ARCH),avr32)
-CROSS_COMPILE = avr32-
+CROSS_COMPILE = avr32-linux-
 endif
 endif
 endif