docs: networking: arcnet-hardware.rst: don't duplicate chapter names

Since changeset 58ad30cf ("docs: fix reference to core-api/namespaces.rst"),
auto-references for chapters are generated. This is a nice feature, but
has a drawback: no chapters can have the same sumber.

So, we need to change two chapter titles, to avoid warnings when
building the docs.

Fixes: 58ad30cf ("docs: fix reference to core-api/namespaces.rst")
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/arcnet-hardware.rst

@@ -1296,8 +1296,8 @@ DIP Switches:
 	11111           0xC400 (guessed - crashes tested system)
 	=============   ============================================
 
-CNet Technology Inc.
-====================
+CNet Technology Inc. (8-bit cards)
+==================================
 
 120 Series (8-bit cards)
 ------------------------
@@ -1520,8 +1520,8 @@ The jumpers labeled EXT1 and EXT2 are used to determine the timeout
 parameters. These two jumpers are normally left open.
 
 
-CNet Technology Inc.
-====================
+CNet Technology Inc. (16-bit cards)
+===================================
 
 160 Series (16-bit cards)
 -------------------------