spi: xilinx: make irq optional

Both the hardware and driver already support polling mode. By removing
the mandatory IRQ requirement during probe, the driver can now fall
back to polling when an interrupt is unavailable, ensuring
compatibility with a wider range of systems.

Signed-off-by: Abdurrahman Hussain <abdurrahman@nexthop.ai>
Link: https://patch.msgid.link/20260119-spi-xilinx-v3-2-4566c33bac0d@nexthop.ai
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: abdurrahman-nexthop

drivers/spi/spi-xilinx.c

@@ -471,7 +471,7 @@ static int xilinx_spi_probe(struct platform_device *pdev)
 	xspi->bytes_per_word = bits_per_word / 8;
 	xspi->buffer_size = xilinx_spi_find_buffer_size(xspi);
 
-	xspi->irq = platform_get_irq(pdev, 0);
+	xspi->irq = platform_get_irq_optional(pdev, 0);
 	if (xspi->irq < 0 && xspi->irq != -ENXIO) {
 		return xspi->irq;
 	} else if (xspi->irq >= 0) {