tools: ynl: Add MAC address parsing support

Add missing support for parsing MAC addresses when display_hint is 'mac'
in the YNL library. This enables YNL CLI to accept MAC address strings
for attributes like lladdr in rt-neigh operations.

Reviewed-by: Donald Hunter <[e-mail]>
Signed-off-by: Hangbin Liu <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

tools/net/ynl/pyynl/lib/ynl.py

···
                 raw = bytes.fromhex(string)
             else:
                 raw = int(string, 16)
+        elif attr_spec.display_hint == 'mac':
+            # Parse MAC address in format "00:11:22:33:44:55" or "001122334455"
+            if ':' in string:
+                mac_bytes = [int(x, 16) for x in string.split(':')]
+            else:
+                if len(string) % 2 != 0:
+                    raise Exception(f"Invalid MAC address format: {string}")
+                mac_bytes = [int(string[i:i+2], 16) for i in range(0, len(string), 2)]
+            raw = bytes(mac_bytes)
         else:
             raise Exception(f"Display hint '{attr_spec.display_hint}' not implemented"
                             f" when parsing '{attr_spec['name']}'")