cpufreq / intel_pstate: Change to disallow module build

Load order is important in order for intel_pstate to take over as the
default scaling driver from acpi-cpufreq.

If both are built-in, acpi-cpufreq uses late_initcall() and
intel_pstate uses device_initcall() so it will be able to register as
the scaling before acpi-cpufreq for the processors supported by
intel_pstate.

If acpi-cpufreq is built as a module then intel_pstate still gets
first option to become the scaling driver.
Signed-off-by: NDirk Brandewie <dirk.j.brandewie@intel.com>
Acked-by: NViresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: NRafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/Kconfig.x86

@@ -3,7 +3,7 @@
 #
 
 config X86_INTEL_PSTATE
-       tristate "Intel P state control"
+       bool "Intel P state control"
        depends on X86
        help
           This driver provides a P state for Intel core processors.
@@ -13,11 +13,6 @@ config X86_INTEL_PSTATE
 	  When this driver is enabled it will become the perferred
           scaling driver for Sandy bridge processors.
 
-	  Note: This driver should be built with the same settings as
-	  the other scaling drivers configured into the system
-	  (module/built-in) in order for the driver to register itself
-	  as the scaling driver on the system.
-
 	  If in doubt, say N.
 
 config X86_PCC_CPUFREQ