lantiq: select PCI support in subtargets

lantiq: select PCI support in subtargets

AmazonSE and Falcon do not have support for PCI and it can't be
unselected in the subtarget kernel config. This way the enabled PCI
support is inherit from the higher level config to the subtarget.

If CONFIG_PCI is selected, PCI_SUPPORT will be autoselected as well and
all packages depending on this config symbol will be build and at least
some of them fail due to missing pci functions.

The issue can be observed if all kmods and all non-shared packages are
build. Fix the issue by enabling PCI support only in subtargets with
PCI support.

Signed-off-by: Mathias Kresin <dev@kresin.me>