kselftest/vDSO: Fix message formatting for clock_id logging

When logging the ID of the currently tested clock vdso_test_clock() puts a
spurious newline at the start of the format string resulting in output
such as

  #
  clock_id: CLOCK_BOOTTIME

which is a valid but empty KTAP informational message followed by a non
conferment output line. Remove the initial newline to create a more KTAP
friendly

  # clock_id: CLOCK_BOOTTIME

Signed-off-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>