mmc: core: Export mmc_set_ios so that host drivers can use it

mmc_set_ios() is used by host drivers during suspend/resume
routines in indirect way i.e., by calling host->ops->set_ios().
But now with MMC_CLKGATE enabled, mmc_set_ios() also updates
host->clk_gated flag. So export this API so that host controller
drivers can use it.

CRs-Fixed: 346559
Signed-off-by: Sujit Reddy Thumma <sthumma@codeaurora.org>
(cherry picked from commit f0410bc6dcacabf599f999f4779091f5cd2c55dc)

Change-Id: Ib7ad7588c1ba4ae5da3ceaaade18caf7c4bdecd1
Signed-off-by: Srivalli Oguri <oguri@codeaurora.org>