dt-bindings: mmc: renesas,sdhi: Rename RZ/G2L clocks

Rename the below RZ/G2L clocks to match with the clock names used in
R-Car Gen2 and later generations.

 imclk->core
 clk_hs->clkh
 imclk2->cd

This changes will avoid using fallback for RZ/G2L high speed clock,
if "clkh" is not used in device tree and also the code changes in
driver related to this clocks.

Signed-off-by: Biju Das <biju.das.jz@bp.renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Acked-by: Ulf Hansson <ulf.hansson@linaro.org>
Link: https://lore.kernel.org/r/20211122103905.14439-2-biju.das.jz@bp.renesas.com


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