PCI: designware-plat: Remove setting epc->features in Designware plat EP driver

Now that pci-epf-test uses get_features callback and
dw_plat_pcie_epc_features in Designware plat EP driver already indicates
it doesn't support linkup notification and is MSIX capable, remove setting
epc->features which is not used anymore by the endpoint function driver.

Tested-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>