doc: netlink: specs: tc: describe flower control flags

Describe the flower control flags, and use them
for key-flags and key-flags-mask.

The flag names have been taken from iproute2.
Suggested-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Asbjørn Sloth Tønnesen <ast@fiberby.net>
Reviewed-by: Donald Hunter <donald.hunter@gmail.com>
Link: https://patch.msgid.link/20240713021911.1631517-3-ast@fiberby.netSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/netlink/specs/tc.yaml

@@ -41,6 +41,12 @@ definitions:
       - in-hw
       - not-in-nw
       - verbose
+  -
+    name: tc-flower-key-ctrl-flags
+    type: flags
+    entries:
+      - frag
+      - firstfrag
   -
     name: tc-stats
     type: struct
@@ -2536,10 +2542,14 @@ attribute-sets:
         name: key-flags
         type: u32
         byte-order: big-endian
+        enum: tc-flower-key-ctrl-flags
+        enum-as-flags: true
       -
         name: key-flags-mask
         type: u32
         byte-order: big-endian
+        enum: tc-flower-key-ctrl-flags
+        enum-as-flags: true
       -
         name: key-icmpv4-code
         type: u8