[CPUFREQ] Fix 'out of sync' issue.

[CPUFREQ] Fix 'out of sync' issue.
Sometimes we might discover during a call to cpufreq_get() that we're "out of sync",
meaning the actual CPU frequency changed "behind our back". If this happens, the flag
CPUFREQ_PANIC_OUTOFSYNC decides what can be done: if it is set, the kernel panic's,
it it is not set, the cpufreq transition notifiers are informed of this change, and
a call to cpufreq_update_policy() is scheduled [using the default workqueue] so that
the user-defined values override BIOS / external interaction.