net: pch_gbe: Use dm_pci_map_bar to discover MMIO base
Reading the PCI BAR & converting the result to a physical address is not
safe across all architectures. For example on MIPS the virtual:physical
mapping is not 1:1, so we cannot directly make use of the physical
address.
Use the more generic BAR-mapping function dm_pci_map_bar to discover the
MMIO base address, which should work across architectures.
Signed-off-by: Paul Burton <paul.burton@imgtec.com> Acked-by: Joe Hershberger <joe.hershberger@ni.com>