According to Figure 52A.1 ("RS-CANFD Module Block Diagram (in classical
CAN mode)") in the R-Car V3U Series User’s Manual Rev. 0.5, the parent
clock for the CANFD peripheral module clock is the S3D2 clock.

Fixes: 9b621b6a ("clk: renesas: r8a779a0: Add CANFD module clock")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/aef9300f44c9141b1465343f91c5cc7303249b6e.1713279523.git.geert+renesas@glider.be