PCI: designware: Rename get_msi_data() to get_msi_addr()

The struct pcie_host_ops .get_msi_data() method returns the MSI message
address.  To accurately express its purpose, rename it to .get_msi_addr().

Signed-off-by: Minghuan Lian <Minghuan.Lian@freescale.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Mohit KUMAR <mohit.kumar@st.com>