Simplify the use of dma_flush_range() by changing its signature to
accept pointer to start of the data and data size. This change allows
us to avoid a whole bunch of repetitive arithmetic currently done by
all of the callers.

Reviewed-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Andrey Smirnov <andrew.smirnov@gmail.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>