cfi_mtd: Fix bug in last sector detection

This patch now enabled this cfi-mtd wrapper to correctly detect and
erase the last sector in an NOR FLASH device.

Signed-off-by: Stefan Roese <sr@denx.de>
diff --git a/drivers/mtd/cfi_mtd.c b/drivers/mtd/cfi_mtd.c
index f03e4fb..4a76917 100644
--- a/drivers/mtd/cfi_mtd.c
+++ b/drivers/mtd/cfi_mtd.c
@@ -43,11 +43,16 @@
 	int s_last = -1;
 	int error, sect;
 
-	for (sect = 0; sect < fi->sector_count - 1; sect++) {
+	for (sect = 0; sect < fi->sector_count; sect++) {
 		if (a_start == fi->start[sect])
 			s_first = sect;
 
-		if (a_end == fi->start[sect + 1]) {
+		if (sect < fi->sector_count - 1) {
+			if (a_end == fi->start[sect + 1]) {
+				s_last = sect;
+				break;
+			}
+		} else {
 			s_last = sect;
 			break;
 		}