Add entries for PCI host controller drivers in drivers/pci/host/.

Signed-off-by: Mohit Kumar <mohit.kumar@st.com>             # DESIGNWARE
Signed-off-by: Pratyush Anand <pratyush.anand@st.com>       # DESIGNWARE
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>
Acked-by: Simon Horman <horms+renesas@verge.net.au>         # R-CAR
Double-Plus-Acked-by: Jason Cooper <jason@lakedaemon.net>   # MVEBU
Acked-by: NJingoo Han <jg1.han@samsung.com>
Acked-by: NThierry Reding <treding@nvidia.com>
Acked-by: NThomas Petazzoni <thomas.petazzoni@free-electrons.com>
Acked-by: Richard Zhu <r65037@freescale.com>                # IMX6