spi: sun4i: update max transfer size reported

The spi-sun4i driver already has the ability to do large transfers.
However, the max transfer size reported is still fifo depth - 1.

Update the max transfer size reported to the max value possible.

Fixes: 19673791 ("spi: sun4i: Allow transfers larger than FIFO size")
Signed-off-by: Jonathan Liu <net147@gmail.com>
Acked-by: Maxime Ripard <mripard@kernel.org>
Link: https://lore.kernel.org/r/20200727072328.510798-1-net147@gmail.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-sun4i.c

@@ -198,7 +198,7 @@ static void sun4i_spi_set_cs(struct spi_device *spi, bool enable)
 
 static size_t sun4i_spi_max_transfer_size(struct spi_device *spi)
 {
-	return SUN4I_FIFO_DEPTH - 1;
+	return SUN4I_MAX_XFER_SIZE - 1;
 }
 
 static int sun4i_spi_transfer_one(struct spi_master *master,