alpha/drm: Cleanup Alpha support in DRM generic code

Remove an obsolete Alpha adjustment, and modify another,
to go with the current Alpha architecture support.

Signed-off-by: Jay Estabrook <jay.estabrook@gmail.com>
Tested-by: Matt Turner <mattst88@gmail.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>
diff --git a/drivers/gpu/drm/drm_vm.c b/drivers/gpu/drm/drm_vm.c
index 2c3fcbd..5db96d45 100644
--- a/drivers/gpu/drm/drm_vm.c
+++ b/drivers/gpu/drm/drm_vm.c
@@ -526,7 +526,7 @@
 static resource_size_t drm_core_get_reg_ofs(struct drm_device *dev)
 {
 #ifdef __alpha__
-	return dev->hose->dense_mem_base - dev->hose->mem_space->start;
+	return dev->hose->dense_mem_base;
 #else
 	return 0;
 #endif