Since sdhci_remove_host() access the device, we need to make sure it's
runtime PM resumed.

To handle clock gating properly in remove, we first have to make sure
the clocks are ungated.

To fix both these issues, by invoking pm_runtime_get_sync() early in
->remove() callback. Later once we disabled runtime PM, we can restore
the usage count.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>