spi/spi-xilinx: Fix mixed poll/irq mode

Once the module process a transfer in irq mode, the next poll transfer
will not work because the transmitter is left in inhibited state.

Fixes: 22417352f6 (Use polling mode on small transfers)
Reported-by: Edward Kigwana <ekigwana@scires.com>
Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@gmail.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
Cc: stable@vger.kernel.org

drivers/spi/spi-xilinx.c

@@ -302,8 +302,10 @@ static int xilinx_spi_txrx_bufs(struct spi_device *spi, struct spi_transfer *t)
 		remaining_words -= n_words;
 	}
 
-	if (use_irq)
+	if (use_irq) {
 		xspi->write_fn(0, xspi->regs + XIPIF_V123B_DGIER_OFFSET);
+		xspi->write_fn(cr, xspi->regs + XSPI_CR_OFFSET);
+	}
 
 	return t->len;
 }