mmc: dw_mmc: Enable low-power mode for the card clock.

Setting this bit in the clock enable register will stop the clock
when the card is in the IDLE state.
Signed-off-by: Will Newton <will.newton@imgtec.com>
Signed-off-by: Chris Ball <cjb@laptop.org>

drivers/mmc/host/dw_mmc.c

@@ -562,7 +562,8 @@ static void dw_mci_setup_bus(struct dw_mci_slot *slot)
 			     SDMMC_CMD_UPD_CLK | SDMMC_CMD_PRV_DAT_WAIT, 0);
 
 		/* enable clock */
-		mci_writel(host, CLKENA, SDMMC_CLKEN_ENABLE);
+		mci_writel(host, CLKENA, SDMMC_CLKEN_ENABLE |
+			   SDMMC_CLKEN_LOW_PWR);
 
 		/* inform CIU */
 		mci_send_cmd(slot,