mmc: rtsx_pci_sdmmc: Don't execute power up sequence repeatedly

For some Realtek card readers, the power up sequence can only be executed
when power has been turned off fully.

So the rtsx host should not start power up sequence again when set_ios
been called if the power has been turned on.

Signed-off-by: Wei WANG <wei_wang@realsil.com.cn>
Signed-off-by: Chris Ball <cjb@laptop.org>