[U-Boot] rockchip: i2c: fix >32 byte reads

[Philipp Tomsich]

> 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 at phytec.de>
> Acked-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>
> ---
>  drivers/i2c/rk_i2c.c | 19 ++++++++++++++++---
>  1 file changed, 16 insertions(+), 3 deletions(-)
> 

Reviewed-by: Philipp Tomsich <philipp.tomsich at theobroma-systems.com>