powernow-k8: Add a kconfig dependency on acpi-cpufreq

Andreas reports in https://bugzilla.kernel.org/show_bug.cgi?id=51741
that with his Gentoo config, acpi-cpufreq wasn't enabled and
powernow-k8 couldn't handoff properly to acpi-cpufreq leading to
running without P-state support (i.e., cores are constantly in P0).

To alleaviate that, we need to make powernow-k8 depend on acpi-cpufreq
so that acpi-cpufreq is always present.

References: https://bugzilla.kernel.org/show_bug.cgi?id=51741
Reported-by: Andreas <linuxuser330250@gmx.net>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: 3.7+ <stable@vger.kernel.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/cpufreq/Kconfig.x86

@@ -106,7 +106,7 @@ config X86_POWERNOW_K7_ACPI
 config X86_POWERNOW_K8
 	tristate "AMD Opteron/Athlon64 PowerNow!"
 	select CPU_FREQ_TABLE
-	depends on ACPI && ACPI_PROCESSOR
+	depends on ACPI && ACPI_PROCESSOR && X86_ACPI_CPUFREQ
 	help
 	  This adds the CPUFreq driver for K8/early Opteron/Athlon64 processors.
 	  Support for K10 and newer processors is now in acpi-cpufreq.