This fixes outdated uart_printf calls and also put the test behind a
console command 'runtest'. The console command returns 'Pass' or 'Fail'.
BUG=chrome-os-partner:18598
TEST=Run pingpong test on Spring
BRANCH=none
Change-Id: Ia2c439685447e42b278556ca66c9f080d4cafe11
Signed-off-by: Vic Yang <victoryang@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/47831
Reviewed-by: Vincent Palatin <vpalatin@chromium.org>