PCI: xilinx-nwl: Add 'Xilinx' to Kconfig prompt

Add the "Xilinx" vendor name to the CONFIG_PCIE_XILINX_NWL Kconfig prompt
so it matches other drivers.  Rename from "PCIe Core" to "PCIe controller".

Link: https://lore.kernel.org/r/20230418174336.145585-4-helgaas@kernel.org


Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
Acked-by: Michal Simek <michal.simek@amd.com>