mmc: sdio: fix nasty oops in mmc_sdio_detect

Power off the card in mmc_sdio_detect __before__ a potential error
handler, which completely removes the card, executes, and only if the
card was successfully powered on beforehand.

While we're at it, use the _sync variant of the runtime PM put API, in
order to ensure that the card is left powered off in case an error
occurred, and the card is going to be removed.

Reproduced and tested on the OLPC XO-1.5.

Reported-by: Daniel Drake <dsd@laptop.org>
Signed-off-by: Ohad Ben-Cohen <ohad@wizery.com>
Signed-off-by: Chris Ball <cjb@laptop.org>