PCI: Let PCI_PRI depend on PCI

This avoids the PCI_PRI question in 'make config' when PCI
is not selected.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>