Add one more bit for OOB (Out Of Band) enabling of P-states.

If OOB handling of P-states is enabled, intel_pstate shouldn't load.
Currently, only "BIT(8) == 1" of the MSR MSR_MISC_PWR_MGMT is
considered as OOB, but "BIT(18) == 1" needs to be taken into
consideration as OOB condition too.
Signed-off-by: Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>
[ rjw: Add an empty code line, edit subject and changelog ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>