nouveau: ACPI support depends on X86 and X86_PLATFORM_DEVICES

If I build nouveau on ia64, Kconfig warns:

warning: (DRM_NOUVEAU) selects ACPI_WMI which has unmet direct dependencies (X86 && X86_PLATFORM_DEVICES && ACPI)
warning: (DRM_NOUVEAU) selects MXM_WMI which has unmet direct dependencies (X86 && X86_PLATFORM_DEVICES && ACPI_WMI)

Make all the ACPI support depend on X86 and select
X86_PLATFORM_DEVICES.

Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/Kconfig b/drivers/gpu/drm/nouveau/Kconfig
index 8a55bee..120e7d1 100644
--- a/drivers/gpu/drm/nouveau/Kconfig
+++ b/drivers/gpu/drm/nouveau/Kconfig
@@ -11,8 +11,9 @@
 	select FRAMEBUFFER_CONSOLE if !EXPERT
 	select FB_BACKLIGHT if DRM_NOUVEAU_BACKLIGHT
 	select ACPI_VIDEO if ACPI && X86 && BACKLIGHT_CLASS_DEVICE && VIDEO_OUTPUT_CONTROL && INPUT
-	select ACPI_WMI if ACPI
-	select MXM_WMI if ACPI
+	select X86_PLATFORM_DEVICES if ACPI && X86
+	select ACPI_WMI if ACPI && X86
+	select MXM_WMI if ACPI && X86
 	select POWER_SUPPLY
 	help
 	  Choose this option for open-source nVidia support.