rockchip: i2c: fix >32 byte reads

The hw can read up to 32 bytes at a time. If we need
more than one chunk, we have to enter the plain RX mode.

Signed-off-by: Wadim Egorov <w.egorov@phytec.de>
Acked-by: Philipp Tomsich <philipp.tomsich@theobroma-systems.com>