mmc: sdhci-of-arasan: add sdhci_arasan_voltage_switch for arasan, 5.1

Per the vendor's requirement, we shouldn't do any setting for
1.8V Signaling Enable, otherwise the interaction/behaviour between
phy and controller will be undefined. Mostly it works fine if we do
that, but we still see failures. Anyway, let's fix it to meet the
vendor's requirement. The error log looks like:

 [   93.405085] mmc1: unexpected status 0x800900 after switch
 [   93.408474] mmc1: switch to bus width 1 failed
 [   93.408482] mmc1: mmc_select_hs200 failed, error -110
 [   93.408492] mmc1: error -110 during resume (card was removed?)
 [   93.408705] PM: resume of devices complete after 213.453 msecs

Signed-off-by: Shawn Lin <shawn.lin@rock-chips.com>
Acked-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>