mmc: sunxi: Set our device drvdata earlier

As soon as the pm_runtime_enable hook is called, our runtime_suspend and
runtime_resume hooks can be called as well. However, we only set the device
drvdata that we will use after we have registered into the MMC core. Move
that earlier so that we don't have a race that could lead to a crash.

Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>