mmc: tmio: Use common error handling code in tmio_mmc_host_probe()

* Add a jump target so that a bit of exception handling can be better
  reused at the end of this function.

* Adjust condition checks.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>