mtd: fix order of TEST/PARTITIONS kconfig options

The MTD_TEST config option was added in between the MTD_PARTITIONS config
and its dependent options which causes the resulting menu system to
display incorrectly as MTD_TEST does not depend on MTD_PARTITIONS.  So
move it up a few lines where it won't cause a problem.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>