dt-bindings: net: dsa: remove obsolete dsa.txt

dsa.txt has been a redirect to dsa.yaml since commit bce58590d1
("dt-bindings: net: dsa: Add DSA yaml binding") introduced the .yaml
schema. The .yaml has the same filename in the same directory, making
this redirect unnecessary for discoverability.

Two files still reference dsa.txt, forcing readers through an extra
hop to reach the .yaml. The stub has not been touched since August
2020. Update references in lan9303.txt and
Documentation/networking/dsa/dsa.rst to point directly to dsa.yaml
and remove the stub.

Signed-off-by: Akash Sukhavasi <akash.sukhavasi@gmail.com>
Acked-by: Rob Herring (Arm) <robh@kernel.org>
Link: https://patch.msgid.link/20260603-b4-remove-redirect-stubs-v2-3-c8c19876ab64@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/devicetree/bindings/net/dsa/dsa.txt

@@ -1,4 +0,0 @@
-Distributed Switch Architecture Device Tree Bindings
-----------------------------------------------------
-
-See Documentation/devicetree/bindings/net/dsa/dsa.yaml for the documentation.

Documentation/devicetree/bindings/net/dsa/lan9303.txt

@@ -16,7 +16,7 @@ Optional properties:
 Subnodes:
 
 The integrated switch subnode should be specified according to the binding
-described in dsa/dsa.txt. The CPU port of this switch is always port 0.
+described in dsa/dsa.yaml. The CPU port of this switch is always port 0.
 
 Note: always use 'reg = <0/1/2>;' for the three DSA ports, even if the device is
 configured to use 1/2/3 instead. This hardware configuration will be

Documentation/networking/dsa/dsa.rst

@@ -509,7 +509,7 @@ Device Tree
 -----------
 
 DSA features a standardized binding which is documented in
-``Documentation/devicetree/bindings/net/dsa/dsa.txt``. PHY/MDIO library helper
+``Documentation/devicetree/bindings/net/dsa/dsa.yaml``. PHY/MDIO library helper
 functions such as ``of_get_phy_mode()``, ``of_phy_connect()`` are also used to query
 per-port PHY specific details: interface connection, MDIO bus location, etc.