PCI: mobiveil: Add Header Type field check

Check the Header Type and exit from the host driver initialization if
it is not in host mode.

Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Andrew Murray <amurray@thegoodpenguin.co.uk>