qoriq_dw_pci: disable LS1028A support

Enabled driver initialization causes an abort
on the NXP LS1028ARDB platform (without any external
endpoints connected). Temporarily disable qoriq_dw_pci
probe, so that to allow successful booting of the OS.

Submitted by: Lukasz Hajec <lha@semihalf.com>
Obtained from: Semihalf
Sponsored by: Alstom Group
Differential Revision: https://reviews.freebsd.org/D30229