PCI: Don't set BAR to zero if dma_addr_t is too small

If a BAR is above 4GB and our dma_addr_t is too small, don't clear the BAR
to zero: that doesn't disable the BAR, and it makes it more likely that the
BAR will conflict with things if we turn on the memory enable bit (as we
will at "out:" if the device was already enabled at the handoff).

We should also print the BAR info and its original size so we can follow
the process when we try to assign space to it.

Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>