mmc: core: Drop unused define for timeout

MMC_CORE_TIMEOUT_MS isn't being used no more, let's drop it.
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>

drivers/mmc/core/core.c

@@ -50,9 +50,6 @@
 #include "sd_ops.h"
 #include "sdio_ops.h"
 
-/* If the device is not responding */
-#define MMC_CORE_TIMEOUT_MS	(10 * 60 * 1000) /* 10 minute timeout */
-
 /* The max erase timeout, used when host->max_busy_timeout isn't specified */
 #define MMC_ERASE_TIMEOUT_MS	(60 * 1000) /* 60 s */