mmc: core: export emmc revision

Expose emmc revision as part of device attributes.
Signed-off-by: Jin Qian <jinqian@android.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

Documentation/ABI/testing/sysfs-bus-mmc

+What:		/sys/bus/mmc/devices/.../rev
+Date:		October 2017
+Contact:	Jin Qian <jinqian@android.com>
+Description:	Extended CSD revision number

drivers/mmc/core/mmc.c

@@ -780,6 +780,7 @@ MMC_DEV_ATTR(manfid, "0x%06x\n", card->cid.manfid);
 MMC_DEV_ATTR(name, "%s\n", card->cid.prod_name);
 MMC_DEV_ATTR(oemid, "0x%04x\n", card->cid.oemid);
 MMC_DEV_ATTR(prv, "0x%x\n", card->cid.prv);
+MMC_DEV_ATTR(rev, "0x%x\n", card->ext_csd.rev);
 MMC_DEV_ATTR(pre_eol_info, "%02x\n", card->ext_csd.pre_eol_info);
 MMC_DEV_ATTR(life_time, "0x%02x 0x%02x\n",
 	card->ext_csd.device_life_time_est_typ_a,
@@ -838,6 +839,7 @@ static struct attribute *mmc_std_attrs[] = {
 	&dev_attr_name.attr,
 	&dev_attr_oemid.attr,
 	&dev_attr_prv.attr,
+	&dev_attr_rev.attr,
 	&dev_attr_pre_eol_info.attr,
 	&dev_attr_life_time.attr,
 	&dev_attr_serial.attr,