wlcore: don't set SDIO_FAILED flag when driver state is off

If some IO read/write fails while the FW is not loaded, a recovery
will not take place. This means the SDIO_FAILED flag will stay in place
forever and prevent further read/writes.

This can happen if a check for STATE_OFF was forgotten in some routine.

Take this opportunity to rename the flag to IO_FAILED, since we support
other buses as well.

Reported-by: Ido Yariv <ido@wizery.com>
Signed-off-by: Arik Nemtsov <arik@wizery.com>