mtd: intflmount: fix off by one error in INFTL_dumpVUchains()

The ->PUtable[] array has "->nb_blocks" number of elemetns so this
comparison should be ">=" instead of ">".  Otherwise it could result in
a minor read beyond the end of an array.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>