anv: Add an anv_physical_device field to anv_device

anv: Add an anv_physical_device field to anv_device

Having to always pull the physical device from the instance has been
annoying for almost as long as the driver has existed.  It also won't
work in a world where we ever have more than one physical device.  This
commit adds a new field called "physical" to anv_device and switches
every location where we use device->instance->physicalDevice to use the
new field instead.

Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/3461>