[CPUFREQ] Fix the bug in duplicate freq elimination code in acpi-cpufreq

Fix the bug in duplicate states elimination in acpi-cpufreq.

Bug: Due to duplicate state elimiation in the loop earlier, the number
of valid_states can be less than perf->state_count, in which case
freq_table was ending up with some garbage/uninitialized entries
in the table.

Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
From:  Alexey Starikovskiy <alexey.y.starikovskiy@intel.com>
Signed-off-by: Dave Jones <davej@redhat.com>