MIPS: Malta: Allow PCI devices DMA to lower 2GB physical

MIPS: Malta: Allow PCI devices DMA to lower 2GB physical

Set the PCI_BAR0 register in all configurations such that PCI devices
can perform DMA to all of the bottom 2GB of the physical address space.
This is imperfect if we make use of the legacy Malta memory map, but it
is an improvement on the inconsistent values setup before.

Signed-off-by: Paul Burton <paul.burton@imgtec.com>
Cc: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/14272/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>