tests/fate/libavutil: switch cpu-test back to runecho so its results are vissible

(needs next commt too)

Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avutil/cpu: output cpu data to stdout

Errors go to stderr, but the cpu stats are non error output for cputest

This fixes echoing the cpu test results

Reviewed-by: James Almer <jamrial@gmail.com>
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>