common: Move reset_phy() to net.h

This is a network function so let's move it into that header.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/freescale/ls2080ardb/eth_ls2080rdb.c b/board/freescale/ls2080ardb/eth_ls2080rdb.c
index 62c7a7a..b0f276e 100644
--- a/board/freescale/ls2080ardb/eth_ls2080rdb.c
+++ b/board/freescale/ls2080ardb/eth_ls2080rdb.c
@@ -6,6 +6,7 @@
 
 #include <common.h>
 #include <command.h>
+#include <net.h>
 #include <netdev.h>
 #include <malloc.h>
 #include <fsl_mdio.h>