imx: nandbcb: Fix potential overflow in fill_dbbt_data

Fix Coverity Issue 9006658. In fill_dbbt_data, an integer overflow occurs,
with the result converted to a wider integer type

Signed-off-by: Ye Li <ye.li@nxp.com>
Reviewed-by: Peng Fan <peng.fan@nxp.com>
Signed-off-by: Peng Fan <peng.fan@nxp.com>
diff --git a/arch/arm/mach-imx/cmd_nandbcb.c b/arch/arm/mach-imx/cmd_nandbcb.c
index 836981c..ea4e147 100644
--- a/arch/arm/mach-imx/cmd_nandbcb.c
+++ b/arch/arm/mach-imx/cmd_nandbcb.c
@@ -476,7 +476,7 @@
 	u32 *n_bad_blocksp = buf + 0x4;
 
 	for (n = 0; n < num_blocks; n++) {
-		loff_t offset = n * mtd->erasesize;
+		loff_t offset = (loff_t)n * mtd->erasesize;
 			if (mtd_block_isbad(mtd, offset)) {
 				n_bad_blocks++;
 				*bb = n;