tools: moveconfig: increment number of processed files monotonically

Currently, the progress " * defconfigs out of 1133" does not increase
monotonically.

Moreover, the number of processed defconfigs does not match the total
number of defconfigs when this tool finishes, like:

 1132 defconfigs out of 1133
Clean up headers? [y/n]:

It looks like the task was not completed, and some users might feel
upset about it.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Joe Hershberger <joe.hershberger@ni.com>