Export sdhci_start_signal_voltage_switch() from sdhci.c.
Thus vendor sdhci driver can implement its own signal voltage
switch routine.
Signed-off-by: NHu Ziji <huziji@marvell.com>
Signed-off-by: NGregory CLEMENT <gregory.clement@free-electrons.com>
Acked-by: NAdrian Hunter <adrian.hunter@intel.com>
Signed-off-by: NUlf Hansson <ulf.hansson@linaro.org>