imx: nandbcb: Fix resource leak in read_fcb

Fix Coverity Issue 9006657. In read_fcb, leak of memory to system
resource "fcb_raw_page". Adjust the sequence to check the mtd bad
block prior than allocation of "fcb_raw_page", also check the NULL
return of allocation.
Signed-off-by: NYe Li <ye.li@nxp.com>
Reviewed-by: NPeng Fan <peng.fan@nxp.com>
Signed-off-by: NPeng Fan <peng.fan@nxp.com>

arch/arm/mach-imx/cmd_nandbcb.c

@@ -503,13 +503,18 @@ static int read_fcb(struct boot_config *boot_cfg, struct fcb_block *fcb,
 	int ret = 0;
 
 	mtd = boot_cfg->mtd;
-	fcb_raw_page = kzalloc(mtd->writesize + mtd->oobsize, GFP_KERNEL);
-
 	if (mtd_block_isbad(mtd, off)) {
 		printf("Block %d is bad, skipped\n", (int)CONV_TO_BLOCKS(off));
 		return 1;
 	}
 
+	fcb_raw_page = kzalloc(mtd->writesize + mtd->oobsize, GFP_KERNEL);
+	if (!fcb_raw_page) {
+		debug("failed to allocate fcb_raw_page\n");
+		ret = -ENOMEM;
+		return ret;
+	}
+
 	/*
 	 * User BCH hardware to decode ECC for FCB
 	 */