drm/amdgpu: fix uninitialized variable pasid_mapping_needed

The boolean variable pasid_mapping_needed is not initialized and
there are code paths that do not assign it any value before it is
is read later.  Fix this by initializing pasid_mapping_needed to
false.

Addresses-Coverity: ("Uninitialized scalar variable")
Fixes: 6817bf28 ("drm/amdgpu: grab the id mgr lock while accessing passid_mapping")
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/amd/amdgpu/amdgpu_vm.c

@@ -1055,7 +1055,7 @@ int amdgpu_vm_flush(struct amdgpu_ring *ring, struct amdgpu_job *job,
 		id->oa_size != job->oa_size);
 	bool vm_flush_needed = job->vm_needs_flush;
 	struct dma_fence *fence = NULL;
-	bool pasid_mapping_needed;
+	bool pasid_mapping_needed = false;
 	unsigned patch_offset = 0;
 	int r;