mmc: mmci: Do pm_runtime_put() after the host has been added

Previously the pm_runtime_put() caused the device to be runtime PM
suspended, but then immediately being resumed when we add the host.

Prevent this unnecessary runtime PM suspend/resume cycle during
->probe() by moving the call to pm_runtime_put() after mmc_add_host().

Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>