It's necessary to setup bus if any slots are present.
- update clock after ctrl reset
- if the host has genpd node, we can guarantee the clock is
  available before starting request. Otherwies, the clock register
  is reset once power off the pd, and host can't output the active
  clock during communication.

Fixes: e9ed8835 ("mmc: dw_mmc: add runtime PM callback")
Fixes: df9bcc2b ("mmc: dw_mmc: add missing codes for runtime resume")
cc: <stable@vger.kernel.org>
Reported-by: Randy Li <randy.li@rock-chips.com>
Reported-by: S. Gilles <sgilles@math.umd.edu>
Signed-off-by: Ziyuan Xu <xzy.xu@rock-chips.com>
Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>