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>

arch/arm/lib/psci-dt.c

@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <asm/cache.h>
 #include <linux/libfdt.h>
 #include <fdt_support.h>
 #include <linux/sizes.h>