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/atmel/at91sam9m10g45ek/at91sam9m10g45ek.c b/board/atmel/at91sam9m10g45ek/at91sam9m10g45ek.c
index 8500431..6df915f 100644
--- a/board/atmel/at91sam9m10g45ek/at91sam9m10g45ek.c
+++ b/board/atmel/at91sam9m10g45ek/at91sam9m10g45ek.c
@@ -7,6 +7,7 @@
 
 #include <common.h>
 #include <debug_uart.h>
+#include <net.h>
 #include <vsprintf.h>
 #include <asm/io.h>
 #include <asm/arch/clk.h>