mtd: mtdcore: use const qualifier

Be a bit stricter and add few more 'const' qualifiers.

Signed-off-by: Artem Bityutskiy <[e-mail]>
Signed-off-by: David Woodhouse <[e-mail]>

drivers/mtd/mtdpart.c

···
  * Do not forget to update 'parse_mtd_partitions()' kerneldoc comment if you
  * are changing this array!
  */
-static const char *default_mtd_part_types[] = {
+static const char * const default_mtd_part_types[] = {
 	"cmdlinepart",
 	"ofpart",
 	NULL