[CPUFREQ] cpufreq_conservative: keep ignore_nice_load and freq_step values when reselected

Keep the value of ignore_nice_load and freq_step of the conservative
governor after the governor is deselected and reselected.

Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Dave Jones <davej@redhat.com>