[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>
diff --git a/drivers/mtd/mtdpart.c b/drivers/mtd/mtdpart.c
index edb90b5..8e77e36 100644
--- a/drivers/mtd/mtdpart.c
+++ b/drivers/mtd/mtdpart.c
@@ -214,7 +214,7 @@
 	instr->addr += part->offset;
 	ret = part->master->erase(part->master, instr);
 	if (ret) {
-		if (instr->fail_addr != 0xffffffff)
+		if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
 			instr->fail_addr -= part->offset;
 		instr->addr -= part->offset;
 	}
@@ -226,7 +226,7 @@
 	if (instr->mtd->erase == part_erase) {
 		struct mtd_part *part = PART(instr->mtd);
 
-		if (instr->fail_addr != 0xffffffff)
+		if (instr->fail_addr != MTD_FAIL_ADDR_UNKNOWN)
 			instr->fail_addr -= part->offset;
 		instr->addr -= part->offset;
 	}