mmc: core: add eMMC hardware reset support

eMMC's may have a hardware reset line.  This patch provides a
host controller operation to implement hardware reset and
a function to reset and reinitialize the card.  Also, for MMC,
the reset is always performed before initialization.

The host must set the new host capability MMC_CAP_HW_RESET
to enable hardware reset.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
diff --git a/include/linux/mmc/host.h b/include/linux/mmc/host.h
index 340cc0c9..b2aefea 100644
--- a/include/linux/mmc/host.h
+++ b/include/linux/mmc/host.h
@@ -151,6 +151,7 @@
 	int	(*execute_tuning)(struct mmc_host *host);
 	void	(*enable_preset_value)(struct mmc_host *host, bool enable);
 	int	(*select_drive_strength)(unsigned int max_dtr, int host_drv, int card_drv);
+	void	(*hw_reset)(struct mmc_host *host);
 };
 
 struct mmc_card;
@@ -233,6 +234,7 @@
 #define MMC_CAP_MAX_CURRENT_600	(1 << 28)	/* Host max current limit is 600mA */
 #define MMC_CAP_MAX_CURRENT_800	(1 << 29)	/* Host max current limit is 800mA */
 #define MMC_CAP_CMD23		(1 << 30)	/* CMD23 supported. */
+#define MMC_CAP_HW_RESET	(1 << 31)	/* Hardware reset */
 
 	mmc_pm_flag_t		pm_caps;	/* supported pm features */