ARM: highbank: enable DMA zone for LPAE

Some devices are restricted to 32-bit DMA. Thus the platform dma_zone_size
needs to be set. Otherwise dma-mapping code is complaining, e.g.

calxedaxgmac fff50000.ethernet: coherent DMA mask 0xffffffff is smaller
than system GFP_DMA mask 0xffffffffffffffff
Signed-off-by: Andreas Herrmann <andreas.herrmann@calxeda.com>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>

arch/arm/mach-highbank/Kconfig

@@ -18,3 +18,4 @@ config ARCH_HIGHBANK
 	select PL320_MBOX
 	select SPARSE_IRQ
 	select USE_OF
+	select ZONE_DMA if ARM_LPAE

arch/arm/mach-highbank/highbank.c

@@ -176,6 +176,9 @@ static const char *highbank_match[] __initconst = {
 };
 
 DT_MACHINE_START(HIGHBANK, "Highbank")
+#if defined(CONFIG_ZONE_DMA) && defined(CONFIG_ARM_LPAE)
+	.dma_zone_size	= (4ULL * SZ_1G),
+#endif
 	.smp		= smp_ops(highbank_smp_ops),
 	.init_irq	= highbank_init_irq,
 	.init_time	= highbank_timer_init,