net: Move initialization of Au1x00 SoC ethernet MAC to cpu_eth_init

This patch will move au1x00_eth_initialize from net/eth.c to cpu_eth_init
as a part of ongoing eth_initialize cleanup work.  The function ret value
is also fixed as it should be negative on fail.

Signed-off-by: Shinya Kuribayashi <skuribay@ruby.dti.ne.jp>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>
diff --git a/cpu/mips/au1x00_eth.c b/cpu/mips/au1x00_eth.c
index 8ddc06a..6272a3a 100644
--- a/cpu/mips/au1x00_eth.c
+++ b/cpu/mips/au1x00_eth.c
@@ -283,7 +283,7 @@
 
 	if ((dev = (struct eth_device*)malloc(sizeof *dev)) == NULL) {
 		puts ("malloc failed\n");
-		return 0;
+		return -1;
 	}
 
 	memset(dev, 0, sizeof *dev);