mmc: tmio: move runtime PM enablement to the driver implementations

Both the Renesas and Uniphier implementations perform actions which
affect runtime PM before calling into the core tmio_mmc_host_probe()
which enabled runtime PM. Move pm_runtime_enable() from the core and
tmio_mmc_host_probe() into each drivers probe() so it can be called
before any clocks or other resources are switched on.

Reported-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>