Moved PPC4xx EMAC driver to drivers/net

Also changed path in all linker scripts that reference this driver

Signed-off-by: Ben Warren <biggerbadderben@gmail.com>
Acked-by: Stefan Roese <sr@denx.de>
diff --git a/board/sbc405/u-boot.lds b/board/sbc405/u-boot.lds
index f3fd56f..08d6f0a 100644
--- a/board/sbc405/u-boot.lds
+++ b/board/sbc405/u-boot.lds
@@ -66,7 +66,7 @@
     cpu/ppc4xx/4xx_uart.o	(.text)
     cpu/ppc4xx/cpu_init.o	(.text)
     cpu/ppc4xx/speed.o	(.text)
-    cpu/ppc4xx/4xx_enet.o	(.text)
+    drivers/net/4xx_enet.o	(.text)
     common/dlmalloc.o	(.text)
     lib_generic/crc32.o		(.text)
     lib_ppc/extable.o	(.text)