MIPS: Octeon: Select ZONE_DMA32

Give us a nice place to allocate coherent DMA memory for 32-bit devices.
Signed-off-by: David Daney <ddaney@caviumnetworks.com>
Patchwork: http://patchwork.linux-mips.org/patch/1635/Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

arch/mips/Kconfig

@@ -691,6 +691,7 @@ config CAVIUM_OCTEON_REFERENCE_BOARD
 	select SWAP_IO_SPACE
 	select HW_HAS_PCI
 	select ARCH_SUPPORTS_MSI
+	select ZONE_DMA32
 	help
 	  This option supports all of the Octeon reference boards from Cavium
 	  Networks. It builds a kernel that dynamically determines the Octeon