intel_pstate: Use LFM bus ratio as min ratio/P state

intel_pstate: Use LFM bus ratio as min ratio/P state

LFM (max efficiency ratio) is the max frequency at minimum voltage
supported by the processor.  Using LFM as the minimum P state
increases performmance without affecting power. By not using P states
below LFM we avoid using P states that are less power efficient.

Signed-off-by: Dirk Brandewie <[email protected]>
Cc: 3.13+ <[email protected]> # 3.13+
Signed-off-by: Rafael J. Wysocki <[email protected]>