PCI: mediatek: Drop excess mtk_pcie.mem kerneldoc description

Struct mtk_pcie.mem was removed by 8a26f861 ("PCI: mediatek: Use
pci_parse_request_of_pci_ranges()"), but the kerneldoc was left.  Remove
the extra kerneldoc.
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

drivers/pci/controller/pcie-mediatek.c

@@ -211,7 +211,6 @@ struct mtk_pcie_port {
  * @base: IO mapped register base
  * @cfg: IO mapped register map for PCIe config
  * @free_ck: free-run reference clock
- * @mem: non-prefetchable memory resource
  * @ports: pointer to PCIe port information
  * @soc: pointer to SoC-dependent operations
  */