mm: sort out the DEVICE_PRIVATE Kconfig mess

The ZONE_DEVICE support doesn't depend on anything HMM related, just on
various bits of arch support as indicated by the architecture.  Also
don't select the option from nouveau as it isn't present in many setups,
and depend on it instead.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Ira Weiny <ira.weiny@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>

drivers/gpu/drm/nouveau/Kconfig

@@ -85,10 +85,10 @@ config DRM_NOUVEAU_BACKLIGHT
 config DRM_NOUVEAU_SVM
 	bool "(EXPERIMENTAL) Enable SVM (Shared Virtual Memory) support"
 	depends on ARCH_HAS_HMM
+	depends on DEVICE_PRIVATE
 	depends on DRM_NOUVEAU
 	depends on STAGING
 	select HMM_MIRROR
-	select DEVICE_PRIVATE
 	default n
 	help
 	  Say Y here if you want to enable experimental support for

mm/Kconfig

@@ -677,13 +677,13 @@ config ARCH_HAS_HMM_MIRROR
 
 config ARCH_HAS_HMM
 	bool
-	default y
 	depends on (X86_64 || PPC64)
 	depends on ZONE_DEVICE
 	depends on MMU && 64BIT
 	depends on MEMORY_HOTPLUG
 	depends on MEMORY_HOTREMOVE
 	depends on SPARSEMEM_VMEMMAP
+	default y
 
 config MIGRATE_VMA_HELPER
 	bool
@@ -709,8 +709,7 @@ config HMM_MIRROR
 
 config DEVICE_PRIVATE
 	bool "Unaddressable device memory (GPU memory, ...)"
-	depends on ARCH_HAS_HMM
-	select HMM
+	depends on ZONE_DEVICE
 	select DEV_PAGEMAP_OPS
 
 	help