mmc: core: Add default timeout value for CMD6

EXT_CSD[248] includes the default maximum timeout for CMD6.
This field is added at eMMC4.5 Spec. And it can be used for default
timeout except for some operations which don't define the timeout
(i.e. background operation, sanitize, flush cache) in eMMC4.5 Spec.

Signed-off-by: Seungwon Jeon <tgih.jun@samsung.com>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
diff --git a/include/linux/mmc/mmc.h b/include/linux/mmc/mmc.h
index 3e0de01..a9e320b 100644
--- a/include/linux/mmc/mmc.h
+++ b/include/linux/mmc/mmc.h
@@ -305,6 +305,7 @@
 #define EXT_CSD_PWR_CL_DDR_52_195	238	/* RO */
 #define EXT_CSD_PWR_CL_DDR_52_360	239	/* RO */
 #define EXT_CSD_POWER_OFF_LONG_TIME	247	/* RO */
+#define EXT_CSD_GENERIC_CMD6_TIME	248	/* RO */
 
 /*
  * EXT_CSD field definitions