dt-bindings: can: rcar_can: Fix R8A7796 SoC name

R8A7796 is R-Car M3-W.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>