The getindex gets increased by one every time. We can calculate the
correct getindex in the driver and avoid the additional reads of rxfs.
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Link: https://lore.kernel.org/all/20221206115728.1056014-6-msp@baylibre.comSigned-off-by: Marc Kleine-Budde <mkl@pengutronix.de>