pci: mediatek: Use PCI_CONF1_EXT_ADDRESS() macro

PCI mediatek driver uses extended format of Config Address for PCI
Configuration Mechanism #1 but with cleared Enable bit.

So use new U-Boot macro PCI_CONF1_EXT_ADDRESS() with clearing
PCI_CONF1_ENABLE bit and remove old custom driver address macros.

Signed-off-by: Pali Rohár <pali@kernel.org>
Reviewed-by: Simon Glass <sjg@chromium.org>