mtd: nand: ecc-bch: Drop mtd_nand_has_bch()

Like for any other compilation option, use the IS_ENABLED() macro
instead of hardcoding it.

By droping this helper we can get rid of the BCH header in nandsim.c.
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20200929230124.31491-7-miquel.raynal@bootlin.com

drivers/mtd/nand/raw/nand_base.c

@@ -5231,7 +5231,7 @@ static int nand_set_ecc_soft_ops(struct nand_chip *chip)
 
 		return 0;
 	case NAND_ECC_ALGO_BCH:
-		if (!mtd_nand_has_bch()) {
+		if (!IS_ENABLED(CONFIG_MTD_NAND_ECC_SW_BCH)) {
 			WARN(1, "CONFIG_MTD_NAND_ECC_SW_BCH not enabled\n");
 			return -EINVAL;
 		}

drivers/mtd/nand/raw/nandsim.c

@@ -23,7 +23,6 @@
 #include <linux/string.h>
 #include <linux/mtd/mtd.h>
 #include <linux/mtd/rawnand.h>
-#include <linux/mtd/nand-ecc-sw-bch.h>
 #include <linux/mtd/partitions.h>
 #include <linux/delay.h>
 #include <linux/list.h>
@@ -2214,7 +2213,7 @@ static int ns_attach_chip(struct nand_chip *chip)
 	if (!bch)
 		return 0;
 
-	if (!mtd_nand_has_bch()) {
+	if (!IS_ENABLED(CONFIG_MTD_NAND_ECC_SW_BCH)) {
 		NS_ERR("BCH ECC support is disabled\n");
 		return -EINVAL;
 	}

include/linux/mtd/nand-ecc-sw-bch.h

@@ -13,8 +13,6 @@ struct nand_chip;
 
 #if IS_ENABLED(CONFIG_MTD_NAND_ECC_SW_BCH)
 
-static inline int mtd_nand_has_bch(void) { return 1; }
-
 /*
  * Calculate BCH ecc code
  */
@@ -37,8 +35,6 @@ void nand_bch_free(struct nand_chip *chip);
 
 #else /* !CONFIG_MTD_NAND_ECC_SW_BCH */
 
-static inline int mtd_nand_has_bch(void) { return 0; }
-
 static inline int
 nand_bch_calculate_ecc(struct nand_chip *chip, const u_char *dat,
 		       u_char *ecc_code)