kernel: Fix off-by-one error in FIT mtd partition search.

This fixes off-by-one error introduced in commit dc76900021
("kernel: Correctly search for the FIT image in mtd partition.")

Function `mtd_read` starts reading at `offset` and
needs `hdr_len` number of bytes to be available. Suppose
the easiest case when `offset` is `0` and `hdr_len` equals
to `mtd->size` - the `for` loop will not be entered even
when enough bytes are available to be read.

Same happens for any non-zero `offset`, when `hdr_len` is
just enough bytes to be read until `mtd->size` is reached.
Imagine that for example `mtd->size=5`, `offset=4` and
`hdr_len=1`. Then `offset+hdr_len=5` and the check has to
be `offset+hdr_len <= mtd->size`, i.e. `5 <= 5`. The
check for `offset + hdr_len` value needs to be inclusive,
therefore use `<=`.

Fixes: dc76900021 ("kernel: Correctly search for the FIT image in mtd partition.")
Signed-off-by: Oldřich Jedlička <oldium.pro@gmail.com>
[adjusted commit ref, fixes tag]
Signed-off-by: Petr Štetiar <ynezz@true.cz>

target/linux/generic/files/drivers/mtd/mtdsplit/mtdsplit_fit.c

@@ -60,7 +60,7 @@ mtdsplit_fit_parse(struct mtd_info *mtd,
 	hdr_len = sizeof(struct fdt_header);
 
 	/* Parse the MTD device & search for the FIT image location */
-	for(offset = 0; offset + hdr_len < mtd->size; offset += mtd->erasesize) {
+	for(offset = 0; offset + hdr_len <= mtd->size; offset += mtd->erasesize) {
 		ret = mtd_read(mtd, offset, hdr_len, &retlen, (void*) &hdr);
 		if (ret) {
 			pr_err("read error in \"%s\" at offset 0x%llx\n",