pci_dw: Trim ATU windows bigger than 4GB

The size of the ATU MEM/IO windows is implicitly casted to uint32_t.
Because of that some window sizes were silently demoted to 0 and ignored.
Check the size if its too large, trim it to 4GB and print a warning message.

Submitted by: Kornel Duleba <mindal@semihalf.com>
Reviewed by: mw
Obtained from: Semihalf
Sponsored by: Marvell
Differential revision: https://reviews.freebsd.org/D29625