ARM: change ARM_DMA_ZONE_SIZE into a variable

Having this value defined at compile time prevents multiple machines with
conflicting definitions to coexist.  Move it to a variable in preparation
for having a per machine value selected at run time.  This is relevant
only when CONFIG_ZONE_DMA is selected.

Signed-off-by: Nicolas Pitre <nicolas.pitre@linaro.org>
2 files changed