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/drivers/net/dwc_eth_qos.c b/drivers/net/dwc_eth_qos.c
index f67c5f4..6db0b5c 100644
--- a/drivers/net/dwc_eth_qos.c
+++ b/drivers/net/dwc_eth_qos.c
@@ -39,6 +39,7 @@
 #include <phy.h>
 #include <reset.h>
 #include <wait_bit.h>
+#include <asm/cache.h>
 #include <asm/gpio.h>
 #include <asm/io.h>
 #include <eth_phy.h>