mtd: mtd_nandecctest: remove unnecessary include

Including linux/jiffies.h was required for calling srandom32(jiffies)
that has already been removed.

Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>