can: j1939: fix address claim code example

During development the define J1939_PGN_ADDRESS_REQUEST was renamed to
J1939_PGN_REQUEST. It was forgotten to adjust the documentation
accordingly.

This patch fixes the name of the symbol.

Reported-by: linux-can/can-utils#159 (comment)
Fixes: 9d71dd0 ("can: add support of SAE J1939 protocol")
Cc: Oleksij Rempel <o.rempel@pengutronix.de>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>

Documentation/networking/j1939.rst

@@ -339,7 +339,7 @@ To claim an address following code example can be used:
 			.pgn = J1939_PGN_ADDRESS_CLAIMED,
 			.pgn_mask = J1939_PGN_PDU1_MAX,
 		}, {
-			.pgn = J1939_PGN_ADDRESS_REQUEST,
+			.pgn = J1939_PGN_REQUEST,
 			.pgn_mask = J1939_PGN_PDU1_MAX,
 		}, {
 			.pgn = J1939_PGN_ADDRESS_COMMANDED,