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>

env/fat.c

@@ -7,6 +7,7 @@
  */
 
 #include <common.h>
+#include <asm/cache.h>
 
 #include <command.h>
 #include <env.h>

env/sf.c

@@ -19,6 +19,7 @@
 #include <search.h>
 #include <errno.h>
 #include <uuid.h>
+#include <asm/cache.h>
 #include <dm/device-internal.h>
 #include <u-boot/crc.h>