X86_POWERNOW_K8_ACPI must depend on ACPI

This patch fixes the following compile error introduced by
commit e8666b27 and reported
by Alexey Dobriyan:

<--  snip  -->

   CC      arch/i386/kernel/acpi/cstate.o
In file included from arch/i386/kernel/acpi/cstate.c:17:
include/acpi/processor.h:88: error: expected specifier-qualifier-list before 'acpi_integer'

<--  snip  -->

If you select something you must ensure that the dependencies of what
you are selecting are fulfilled.
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Cc: Alexey Dobriyan <adobriyan@sw.ru>
Cc: Joshua Hoblitt <jhoblitt@ifa.hawaii.edu>
Cc: Dave Jones <davej@redhat.com>
Cc: Michal Piotrowski <michal.k.k.piotrowski@gmail.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/i386/kernel/cpu/cpufreq/Kconfig

@@ -92,7 +92,7 @@ config X86_POWERNOW_K8
 config X86_POWERNOW_K8_ACPI
 	bool "ACPI Support"
 	select ACPI_PROCESSOR
-	depends on X86_POWERNOW_K8
+	depends on ACPI && X86_POWERNOW_K8
 	default y
 	help
 	  This provides access to the K8s Processor Performance States via ACPI.