libtimeinstate: correctly handle devices with no boost freqs

initGlobals() should only fail if a cpufreq policy doesn't report any
frequencies at all; if scaling_available_frequencies reports some
freqs then it's fine if scaling_boost_frequencies is absent

Bug: 138317993
Test: libtimeinstate_test passes on a device with no boost freqs
Change-Id: I3fe0f2fbdf61888406a687ba4016f9bf7fe4796a
Signed-off-by: Connor O'Brien <connoro@google.com>