mn10300: Select CONFIG_HAVE_UID16 to fix build failure

mn10300: Select CONFIG_HAVE_UID16 to fix build failure

mn10300 builds fail with

fs/stat.c: In function 'cp_old_stat':
fs/stat.c:163:2: error: 'old_uid_t' undeclared

ipc/util.c: In function 'ipc64_perm_to_ipc_perm':
ipc/util.c:540:2: error: 'old_uid_t' undeclared

Select CONFIG_HAVE_UID16 and remove local definition of CONFIG_UID16
to fix the problem.

Fixes: fbc416ff8618 ("arm64: fix building without CONFIG_UID16")
Cc: Arnd Bergmann <arnd@arndb.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>