firmware_DevScreenTimeout: Relax error margin

Current margin (3 seconds) is too small and thus if the device
initialize too fast, the test will fail incorrectly. Let's relax the
margin to 5 seconds.

BUG=chrome-os-partner:13530
TEST=none

Change-Id: If931902a90e730667d4b959f4a9c2518c7b49a5a
Signed-off-by: Vic Yang <victoryang@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/32689
Reviewed-by: Tom Wai-Hong Tam <waihong@chromium.org>
1 file changed