anv: Initialize anv_bo::offset to -1

Since -1 is an invalid GPU address, this lets us know whether or not we
have a valid address for a buffer.  We don't get a valid address until the
first time that buffer is used in an execbuf2 ioctl.

Signed-off-by: Jason Ekstrand <jason@jlekstrand.net>
Reviewed-by: Kristian H. Kristensen <hoegsberg@google.com>
Cc: "13.0" <mesa-stable@lists.freedesktop.org>

src/intel/vulkan/anv_private.h

@@ -275,7 +275,7 @@ anv_bo_init(struct anv_bo *bo, uint32_t gem_handle, uint64_t size)
 {
    bo->gem_handle = gem_handle;
    bo->index = 0;
-   bo->offset = 0;
+   bo->offset = -1;
    bo->size = size;
    bo->map = NULL;
    bo->is_winsys_bo = false;