mtd: nand: fix mention to CONFIG_MTD_NAND_ECC_BCH

Mention to CONFIG_MTD_ECC_BCH in the warning message can be confusing as this
doesn't match the exact name of the configuration option.
This warning showed up once to me when I was starting to set up BCH. After
checking my .config file, it took a moment before realizing it is
CONFIG_MTD_NAND_ECC_BCH instead of CONFIG_MTD_ECC_BCH.

Signed-off-by: Erico Nunes <nunes.erico@gmail.com>
Acked-by: Lee Jones <lee.jones@linaro.org>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/nand_base.c

@@ -3925,7 +3925,7 @@ int nand_scan_tail(struct mtd_info *mtd)
 
 	case NAND_ECC_SOFT_BCH:
 		if (!mtd_nand_has_bch()) {
-			pr_warn("CONFIG_MTD_ECC_BCH not enabled\n");
+			pr_warn("CONFIG_MTD_NAND_ECC_BCH not enabled\n");
 			BUG();
 		}
 		ecc->calculate = nand_bch_calculate_ecc;