PCI/MSI: Simplify msi_verify_entries()

No point in looping over all entries when 64bit addressing mode is enabled
for nothing.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Marc Zyngier <maz@kernel.org>
Reviewed-by: Marc Zyngier <maz@kernel.org>
Acked-by: Bjorn Helgaas <bhelgaas@google.com>
Link: https://lore.kernel.org/r/20210729222542.992849326@linutronix.de