pci: Make is_bridge a bool

pci: Make is_bridge a bool

The is_bridge field in PCIDevice acts as a bool, but is declared as an int.
Declare it as a bool for clarity, and change everything that writes it to
use true/false instead of 0/1 to match.

Signed-off-by: David Gibson <[email protected]>
Reviewed-by: Greg Kurz <[email protected]>
Message-Id: <20190513061939[email protected]>
Reviewed-by: Michael S. Tsirkin <[email protected]>
Signed-off-by: Michael S. Tsirkin <[email protected]>