mtd: nand: omap: fix compile warning on ‘erased_sector_bitflips’

Commit 2c9f2365 (mtd: nand: omap: ecc.calculate: merge omap3_calculate_ecc_bch4
in omap_calculate_ecc_bch) introduced minor compile warning
"‘erased_sector_bitflips’ defined but not used [-Wunused-function]" when
compiling without CONFIG_MTD_NAND_OMAP_BCH. Move function
erased_sector_bitflips() into the same ifdef section as the only caller.
Signed-off-by: Christian Engelmayer <cengelma@gmx.at>
Reviewed-by: Jingoo Han <jg1.han@samsung.com>
Acked-by: Pekon Gupta <pekon@ti.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>

drivers/mtd/nand/omap2.c

@@ -1237,6 +1237,7 @@ static int __maybe_unused omap_calculate_ecc_bch(struct mtd_info *mtd,
 	return 0;
 }
 
+#ifdef CONFIG_MTD_NAND_OMAP_BCH
 /**
  * erased_sector_bitflips - count bit flips
  * @data:	data sector buffer
@@ -1276,7 +1277,6 @@ static int erased_sector_bitflips(u_char *data, u_char *oob,
 	return flip_bits;
 }
 
-#ifdef CONFIG_MTD_NAND_OMAP_BCH
 /**
  * omap_elm_correct_data - corrects page data area in case error reported
  * @mtd:	MTD device structure