common: Drop net.h from common header

Move this header out of the common header. Network support is used in
quite a few places but it still does not warrant blanket inclusion.

Note that this net.h header itself has quite a lot in it. It could be
split into the driver-mode support, functions, structures, checksumming,
etc.

Signed-off-by: Simon Glass <sjg@chromium.org>

net/bootp.c

@@ -13,6 +13,7 @@
 #include <env.h>
 #include <efi_loader.h>
 #include <net.h>
+#include <rand.h>
 #include <uuid.h>
 #include <net/tftp.h>
 #include "bootp.h"