mmc: sdio: Move comment about re-initialization to mmc_sdio_reinit_card()

The comment in mmc_sdio_power_restore() belongs in mmc_sdio_reinit_card(),
which was created during a previous commit that re-factored some code. Fix
this by moving the comment into mmc_sdio_reinit_card().

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
Reviewed-by: Douglas Anderson <dianders@chromium.org>