[MTD] [NAND] Fix an off-by-one in a BUG_ON in CAFÉ ECC correction.

err_pos_lut[4096] of an array with 4096 elements is a bug.

Spotted by the Coverity checker.

While I was at it, I also converted it to ARRAY_SIZE().
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

drivers/mtd/nand/cafe_ecc.c

@@ -1045,7 +1045,7 @@ static unsigned short err_pos_lut[4096] = {
 
 static unsigned short err_pos(unsigned short din)
 {
-	BUG_ON(din > 4096);
+	BUG_ON(din >= ARRAY_SIZE(err_pos_lut));
 	return err_pos_lut[din];
 }
 static int chk_no_err_only(unsigned short *chk_syndrome_list, unsigned short *err_info)