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>

common/usb_storage.c

@@ -39,6 +39,7 @@
 #include <mapmem.h>
 #include <memalign.h>
 #include <asm/byteorder.h>
+#include <asm/cache.h>
 #include <asm/processor.h>
 #include <dm/device-internal.h>
 #include <dm/lists.h>