[MTD] Define and use MTD_FAIL_ADDR_UNKNOWN instead of 0xffffffff

Signed-off-by: Adrian Hunter <ext-adrian.hunter@nokia.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

include/linux/mtd/mtd.h

@@ -25,8 +25,10 @@
 #define MTD_ERASE_DONE          0x08
 #define MTD_ERASE_FAILED        0x10
 
+#define MTD_FAIL_ADDR_UNKNOWN 0xffffffff
+
 /* If the erase fails, fail_addr might indicate exactly which block failed.  If
-   fail_addr = 0xffffffff, the failure was not at the device level or was not
+   fail_addr = MTD_FAIL_ADDR_UNKNOWN, the failure was not at the device level or was not
    specific to any particular block. */
 struct erase_info {
 	struct mtd_info *mtd;