mfd: tmio: Remove obsolete .set_clk_div() callback

mfd: tmio: Remove obsolete .set_clk_div() callback

Commit bef64d2908e825c5 ("mmc: remove tmio_mmc driver") removed the last
user of the .set_clk_div() callback in the tmio_mmc_data structure.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Tested-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Acked-by: Lee Jones <lee@kernel.org>
Link: https://lore.kernel.org/r/e0fa98f138a7b2836128178f8b3a757978517307.1718897545.git.geert+renesas@glider.be
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>