perf tests: Replace assignment with comparison on assert check

perf tests: Replace assignment with comparison on assert check

The current assert check is checking an assignment, which will always be
true.  Instead, the assert should be checking if scale is equal to 0.122

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Masami Hiramatsu <mhiramat@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1461419154-16918-1-git-send-email-colin.king@canonical.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>