mtd: partitions: make parsers return 'const' partition arrays

We only want to modify these arrays inside the parser "drivers", so the
drivers should construct them however they like, then return them as
immutable arrays.

This will make other refactorings easier.

Signed-off-by: Brian Norris <computersforpeace@gmail.com>
Reviewed-by: Boris Brezillon <boris.brezillon@free-electrons.com>

drivers/mtd/cmdlinepart.c

@@ -304,7 +304,7 @@ static int mtdpart_setup_real(char *s)
  * the first one in the chain if a NULL mtd_id is passed in.
  */
 static int parse_cmdline_partitions(struct mtd_info *master,
-				    struct mtd_partition **pparts,
+				    const struct mtd_partition **pparts,
 				    struct mtd_part_parser_data *data)
 {
 	unsigned long long offset;