[CPUFREQ] Powernow-k8: Enable more than 2 low P-states

Remove an obsolete check that used to prevent there being more
than 2 low P-states.  Now that low-to-low P-states changes are
enabled, it prevents otherwise workable configurations with
multiple low P-states.

Signed-off-by: Mark Langsdorf <mark.langsdorf@amd.com>
Tested-by: Krists Krilovs <pow@pow.za.net>
Signed-off-by: Dave Jones <davej@redhat.com>