arm: Set NEW_PCIB in DEFAULTS rather than a subset of kernel configs

All other architectures set NEW_PCIB in DEFAULTS, with arm being the one
remaining straggler that only sets it for GENERIC and TEGRA124.
ARMADA38X and ARMADAXP contain device pci but don't set NEW_PCIB,
however GENERIC claims to support them and as part of that NEW_PCIB
support was added to mv_pci, so these configs are most likely just
stale. Other than NOTES that just leaves ALPINE as the one kernel with
PCI support not covered by GENERIC, but al_pci is supported by arm64
which enables NEW_PCIB, and it's just a generic_pcie_fdt_driver with
some fixup code to deal with quirks so should support PCI_RES_BUS just
fine. Therefore it is believed that all in-tree kernel configs support
NEW_PCIB in reality, and so let's take a step towards removing all the
non-NEW_PCIB code by having it always-on everywhere.

Reviewed by: emaste, jhb, manu
MFC after: 1 month
Differential Revision: https://reviews.freebsd.org/D43806