PCI: designware: Remove redundant call to pci_write_config_word()

write_msi_msg() does exactly the same so there is no need to explicitly
call pci_write_config_word() and do the same twice.

Tested-by: Mohit Kumar <mohit.kumar@st.com>
Signed-off-by: Bjørn Erik Nilsen <ben@datarespons.no>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Marek Vasut <marex@denx.de>
Acked-by: Jingoo Han <jg1.han@samsung.com>