PCI: controller: dwc: Do not let PCIE_DW_PLAT_HOST default to yes

PCIE_DW_PLAT_HOST does not have any platform dependency, so it should
not default to yes.

Fixes: 1d906b22 ("PCI: dwc: Add support for EP mode")
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Gustavo Pimentel <gustavo.pimentel@synopsys.com>