doc: net: fix bad references to network drivers

Fix "reference to nonexisting document" warnings.

Fixes: b255e500 ("net: documentation: build a directory structure for drivers")
Signed-off-by: NOtto Sabart <ottosabart@seberm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Documentation/networking/index.rst

@@ -11,19 +11,19 @@ Contents:
    batman-adv
    can
    can_ucan_protocol
-   dpaa2/index
-   e100
-   e1000
-   e1000e
-   fm10k
-   igb
-   igbvf
-   ixgb
-   ixgbe
-   ixgbevf
-   i40e
-   iavf
-   ice
+   device_drivers/freescale/dpaa2/index
+   device_drivers/intel/e100
+   device_drivers/intel/e1000
+   device_drivers/intel/e1000e
+   device_drivers/intel/fm10k
+   device_drivers/intel/igb
+   device_drivers/intel/igbvf
+   device_drivers/intel/ixgb
+   device_drivers/intel/ixgbe
+   device_drivers/intel/ixgbevf
+   device_drivers/intel/i40e
+   device_drivers/intel/iavf
+   device_drivers/intel/ice
    kapi
    z8530book
    msg_zerocopy