tf-a-artifacts-cleanup: Process build.log's in batches of 1000

The initial idea was to avoid spikes of high disk usage by processing in
100s, but we have too many files, so would need to run that more regularly.
For now, just use bigger batches.

Signed-off-by: Paul Sokolovsky <paul.sokolovsky@linaro.org>
Change-Id: Id1805b6920d0392ebe450cf38b3f5bece2050b4d
1 file changed