clk: renesas: r8a7795: Add 3DGE and ZG support

The 3DGE and ZG clocks are necessary to support the 3D graphics.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/36096e2df2a54516fadd1978c47fc7de354abc26.1689599217.git.geert+renesas@glider.be