DMA is preferred for a larger transfers, while PIO is preferred for a
smaller transfers to avoid unnecessary DMA overhead. There is no strict
size limitations for the PIO-mode transfers, so let's rename the constant
for clarity.
Tested-by: NThierry Reding <treding@nvidia.com>
Signed-off-by: NDmitry Osipenko <digetx@gmail.com>
Signed-off-by: NWolfram Sang <wsa@the-dreams.de>