pci-assign: propagate Error from check_irqchip_in_kernel()

Rename check_irqchip_in_kernel() to verify_irqchip_in_kernel(), so that
the name reflects our expectation better. Rather than returning a bool,
make it do nothing or set an Error.

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
