mmc: renesas_sdhi: remove a stale comment

The whitelist has been refactored away with a0fb3fc8 ("mmc:
renesas_sdhi: remove whitelist for internal DMAC") so the comment
doesn't make any sense anymore.

Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/20220320123016.57991-5-wsa+renesas@sang-engineering.com


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>