ring_buffer.c

To avoid bounce buffer when an i2c controller decides to use DMA for a
transaction, let's make out buffer that we use for reads DMA-safe and let
the master know that DMAing into it is safe.

Signed-off-by: Stephen Boyd <swboyd@chromium.org>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>