mmc: tmio: Remove obsolete .set_pwr() callback()

mmc: tmio: Remove obsolete .set_pwr() callback()

Commit ca78476e4888f1f1 ("mfd: Remove toshiba tmio drivers") removed the
last users of the .set_pwr() callback in the tmio_mmc_data structure.
Remove the callback, and all related infrastructure.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Acked-by: Lee Jones <lee@kernel.org>
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>
Link: https://lore.kernel.org/r/fbbc13ddd19df2c40933ffa3b82fb14841bf1d4c.1718897545.git.geert+renesas@glider.be