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>

board/eric/u-boot.lds

@@ -68,7 +68,7 @@ SECTIONS
     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)