Both  Renesas R-Car and RZ/A1 manuals state that RX buffer  length must be
a multiple of 32 bytes, while the driver  only uses 16 byte granularity...
Signed-off-by: NSergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>