mtd: nand: add __nand_correct_data helper function

Split nand_correct_data() into two part, a pure calculation function
and a wrapper for mtd interface.

The tmio_nand driver can implement its ecc.correct function easily
using this __nand_correct_data helper.

Signed-off-by: Atsushi Nemoto <anemo@mba.ocn.ne.jp>
Acked-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Acked-by: Vimal Singh <vimalsingh@ti.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/include/linux/mtd/nand_ecc.h b/include/linux/mtd/nand_ecc.h
index 090da50..052ea8c 100644
--- a/include/linux/mtd/nand_ecc.h
+++ b/include/linux/mtd/nand_ecc.h
@@ -21,6 +21,12 @@
 int nand_calculate_ecc(struct mtd_info *mtd, const u_char *dat, u_char *ecc_code);
 
 /*
+ * Detect and correct a 1 bit error for eccsize byte block
+ */
+int __nand_correct_data(u_char *dat, u_char *read_ecc, u_char *calc_ecc,
+			unsigned int eccsize);
+
+/*
  * Detect and correct a 1 bit error for 256 byte block
  */
 int nand_correct_data(struct mtd_info *mtd, u_char *dat, u_char *read_ecc, u_char *calc_ecc);