devices: vvu: split proxy bar
devices: vvu: split proxy bar

Split the proxy device's bar into a non-prefetchable bar for the
doorbell and notifications and a prefetchable bar for sibling memory.
This diverges from the specifics of the qemu implementation, but it
should still be compliant with the VVU spec.

BUG=None
TEST=boot crostini on brya-manatee

Change-Id: I5bb63a70907504aa1f286535dbcfe67c19e35b68
Reviewed-on: https://chromium-review.googlesource.com/c/crosvm/crosvm/+/3802640
Reviewed-by: Keiichi Watanabe <815e4e8f7c92a23424d7c3f51ead622bcedbc720@chromium.org>
Commit-Queue: David Stevens <2f87ba95ff5d327328bd68c2e86a4d9f2ba99bd0@chromium.org>
Tested-by: David Stevens <2f87ba95ff5d327328bd68c2e86a4d9f2ba99bd0@chromium.org>
Reviewed-by: Alexandre Courbot <301cd6a3ea50a894b4b51e385c5eb12b9a4ffc0c@chromium.org>

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