drm/xe: Fix checking for unset value

Commit 37430402 ("drm/xe: NULL binding implementation") introduced
the NULL binding implementation, but left a case in which the out value
is_vram is not set and the caller will use whatever was on stack.
Eventually the is_vram out could be removed, but this should at least
fix the current bug.

Fixes: 37430402 ("drm/xe: NULL binding implementation")
Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Link: https://lore.kernel.org/r/20230726160708.3967790-4-lucas.demarchi@intel.comSigned-off-by: Lucas De Marchi <lucas.demarchi@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_pt.c

@@ -81,8 +81,10 @@ u64 xe_pde_encode(struct xe_bo *bo, u64 bo_offset,
 static dma_addr_t vma_addr(struct xe_vma *vma, u64 offset,
 			   size_t page_size, bool *is_vram)
 {
-	if (xe_vma_is_null(vma))
+	if (xe_vma_is_null(vma)) {
+		*is_vram = 0;
 		return 0;
+	}
 
 	if (xe_vma_is_userptr(vma)) {
 		struct xe_res_cursor cur;