powerpc/44x: Force PCI on for CURRITUCK

The recent rework of PCI kconfig symbols exposed an existing bug in
the CURRITUCK kconfig logic.

It selects PPC4xx_PCI_EXPRESS which depends on PCI, but PCI is user
selectable and might be disabled, leading to a warning:

  WARNING: unmet direct dependencies detected for PPC4xx_PCI_EXPRESS
    Depends on [n]: PCI [=n] && 4xx [=y]
    Selected by [y]:
    - CURRITUCK [=y] && PPC_47x [=y]

Prior to commit eb01d42a ("PCI: consolidate PCI config entry in
drivers/pci") PCI was enabled by default for currituck_defconfig so we
didn't see the warning. The bad logic was still there, it just
required someone disabling PCI in their .config to hit it.

Fix it by forcing PCI on for CURRITUCK, which seems was always the
expectation anyway.

Fixes: eb01d42a ("PCI: consolidate PCI config entry in drivers/pci")
Reported-by: Randy Dunlap <rdunlap@infradead.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>