mmc: host: omap-hsmmc: remove init_card pdata callback from pdata

Now as we have removed the last user (pandora_wl1251_init_card)
of this callback, we can remove it from the hsmmc code.

Suggested-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: H. Nikolaus Schaller <hns@goldelico.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>