PCI: designware-ep: Fix the Header Type check

The current check will result in the multiple function device
fails to initialize. So fix the check by masking out the
multiple function bit.

Link: https://lore.kernel.org/r/20200818092746.24366-1-Zhiqiang.Hou@nxp.com


Fixes: 0b24134f ("PCI: dwc: Add validation that PCIe core is set to correct mode")
Signed-off-by: Hou Zhiqiang <Zhiqiang.Hou@nxp.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Reviewed-by: Rob Herring <robh@kernel.org>