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>
diff --git a/common/spl/spl_atf.c b/common/spl/spl_atf.c
index 702367b..bc2921c 100644
--- a/common/spl/spl_atf.c
+++ b/common/spl/spl_atf.c
@@ -14,6 +14,7 @@
 #include <cpu_func.h>
 #include <errno.h>
 #include <spl.h>
+#include <asm/cache.h>
 
 static struct bl2_to_bl31_params_mem bl31_params_mem;
 static struct bl31_params *bl2_to_bl31_params;