configs: sandbox64: Enable PCI register multi-entry support

Align the sandbox64 defconfig with sandbox defconfig. Enable missing
PCI register multi-entry support. This fixes ut_dm_dm_test_pci_bus_to_phys
test .

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Simon Glass <sjg@chromium.org>