Add device nodes for the remaining High Speed Serial Communication
Interfaces with FIFO (HSCIF) on the Renesas R-Car V4M (R8A779H0) SoC,
including DMA support and the optional external clock source used by
HSCIF2.

Based on a patch in the BSP by Nghia Nguyen.
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/b39f081db01fde2d1bf83a193f25b295cfeb002d.1709741303.git.geert+renesas@glider.be