arm64: dts: renesas: r8a77965: Add CAN{0,1} placeholder nodes

According to R-Car Gen3 HW manual rev1.00, R-Car M3-N has two CAN
interfaces, similar to H3, M3-W and other SoCs from the same family.

Add CAN placeholder nodes to avoid below DTC errors:
Error: arch/arm64/boot/dts/renesas/ulcb-kf.dtsi:19.1-6 Label or path can0 not found
Error: arch/arm64/boot/dts/renesas/ulcb-kf.dtsi:25.1-6 Label or path can1 not found

These errors occur *after* the addition of r8a77965-m3nulcb-kf.dts.
Fix them beforehand.

CAN support is inspired from below commits:
 - v4.7 commit 308b7e4b ("arm64: dts: r8a7795: Add CAN support")
 - v4.11 commit 909c1625 ("arm64: dts: r8a7796: Add CAN support")
 - v4.12 commit bec0948e ("arm64: dts: r8a7796: Add reset control properties")

Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Kieran Bingham <kieran.bingham+renesas@ideasonboard.com>
[simon: make placeholder minimal by only including reg property]
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>