Correct subsystem_{vendor,id} mixup in StubPciDevice
Correct subsystem_{vendor,id} mixup in StubPciDevice

BUG=None
TEST=New unit test.

Change-Id: Idfe19e5d2f1625e7c76f390928342f02f0d17cff
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/3308807
Auto-Submit: Mattias Nissler <f2124f8e21694335a48d099eb9510c5c4dda0d0b@chromium.org>
Tested-by: kokoro <2ac7b1f3fa578934c95181d4272be0d3bca00121@google.com>
Commit-Queue: Mattias Nissler <f2124f8e21694335a48d099eb9510c5c4dda0d0b@chromium.org>
Reviewed-by: Daniel Verkamp <72bc170b46ec491f7bdd4359a1c0bfed274de40c@chromium.org>

google/crosvm,google/crosvm,google/crosvm,google/crosvm