rusticl: reset VMA address of resource inside SVMAlloc::drop

If we want to use of the internal refcounting of pipe_resources, we have
to stop setting the resources's SVM address to 0 inside
PipeResource::drop.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/35812>

src/gallium/frontends/rusticl/core/context.rs

@@ -68,6 +68,12 @@ impl Drop for SVMAlloc {
                 debug_assert_eq!(0, ret);
             }
 
+            for (dev, res) in &self.alloc.get_real_resource().res {
+                if !dev.system_svm_supported() {
+                    dev.screen().resource_assign_vma(res, 0);
+                }
+            }
+
             Platform::get()
                 .vm
                 .as_ref()

src/gallium/frontends/rusticl/core/memory.rs

@@ -499,7 +499,7 @@ impl Allocation {
     }
 
     /// Follows the sub-allocation chain until it hits a real GPU allocation.
-    fn get_real_resource(&self) -> &ResourceAllocation {
+    pub fn get_real_resource(&self) -> &ResourceAllocation {
         match self {
             Allocation::SubAlloc(sub) => sub.mem.alloc.get_real_resource(),
             Allocation::Resource(res) => res,

src/gallium/frontends/rusticl/mesa/pipe/resource.rs

@@ -285,15 +285,6 @@ impl PipeResource {
 impl Drop for PipeResource {
     fn drop(&mut self) {
         unsafe {
-            let pipe = self.pipe.as_ref();
-            let screen = pipe.screen.as_ref().unwrap();
-
-            if pipe.flags & PIPE_RESOURCE_FLAG_FRONTEND_VM != 0 {
-                if let Some(resource_assign_vma) = screen.resource_assign_vma {
-                    resource_assign_vma(pipe.screen, self.pipe(), 0);
-                }
-            }
-
             pipe_resource_reference(&mut self.pipe.as_ptr(), ptr::null_mut());
         }
     }