sun6i spi driver issue

[Sergey Suloev]

Hi,

the following patch [1] isn't working on my BPi M2, OPi PC, OPi PC+. I 
have no more boards to test currently but I am sure it will fail on 
others too. As soon as the max transfer size is set to a value MORE THAN 
FIFO then most of transfers would end up with -110 (timeout).

[1] https://patchwork.kernel.org/patch/9634315/

I have reverted the patch back in my local kernel and it works well on 
all the boards mentioned. It works fine too without subtracting 1 byte 
from FIFO, i.e. one could use the code below:

static size_t sun6i_spi_max_transfer_size(struct spi_device *spi)
{
         struct sun6i_spi *sspi = spi_master_get_devdata(spi->master);

         return sspi->fifo_depth;
}

Thanks