clk: renesas: r8a779a0: Add the DSI clocks

The DSI clock is incorrectly defined as a fixed clock. This
demonstrates itself as the dsi-encoders failing to correctly enable and
start their PPI and HS clocks internally, and causes failures.

Move the DSI parent clock to match the updates in the BSP, which
resolves the initialisation procedures.

Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>
Fixes: 17bcc803 ("clk: renesas: cpg-mssr: Add support for R-Car V3U")
Link: https://lore.kernel.org/r/20210622232711.3219697-3-kieran.bingham@ideasonboard.com


Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>