mmc: fix detection of memory part of SD-combo card with broken SDIO

In case of failure, mmc_attach_sdio() will power off the SD bus.
Power it up and reinitialize before trying SD memory detection.

Reported-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Reviewed-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Chris Ball <cjb@laptop.org>