perf bench numa: Fix type of loop iterator in do_work, it should be 'long'

'j' is of type int and start/end are of type 'long'. Thus 'j' might become
negative and cause segfault in access_data(). Fix it by using 'long' for
'j' as well.

Reviewed-by: James Clark <james.clark@arm.com>
Signed-off-by: Andreas Herrmann <aherrmann@suse.de>
Link: https://lore.kernel.org/r/20230330074202.14052-1-aherrmann@suse.de


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>