clk: renesas: rcar-gen3: Remove stp_ck handling for SDHI

There is no case (and none foreseen) where we would need to disable the
SDn clock. So, for simplicity, remove its handling.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/r/20200922120036.10298-1-wsa+renesas@sang-engineering.com


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