spi: s3c64xx: fix NULL-deref on driver unbind

A change moving DMA channel allocation from probe() back to
s3c64xx_spi_prepare_transfer() failed to remove the corresponding
deallocation from remove().

Drop the bogus DMA channel release from remove() to avoid triggering a
NULL-pointer dereference on driver unbind.

This issue was flagged by Sashiko when reviewing a controller
deregistration fix.

Fixes: f52b03c ("spi: s3c64xx: requests spi-dma channel only during data transfer")
Cc: stable@vger.kernel.org	# 6.0
Cc: Adithya K V <adithya.kv@samsung.com>
Link: https://sashiko.dev/#/patchset/20260410081757.503099-1-johan%40kernel.org
Signed-off-by: Johan Hovold <johan@kernel.org>
Link: https://patch.msgid.link/20260410094925.518343-1-johan@kernel.org
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: jhovold

drivers/spi/spi-s3c64xx.c

@@ -1403,11 +1403,6 @@ static void s3c64xx_spi_remove(struct platform_device *pdev)
 
 	writel(0, sdd->regs + S3C64XX_SPI_INT_EN);
 
-	if (!is_polling(sdd)) {
-		dma_release_channel(sdd->rx_dma.ch);
-		dma_release_channel(sdd->tx_dma.ch);
-	}
-
 	pm_runtime_put_noidle(&pdev->dev);
 	pm_runtime_disable(&pdev->dev);
 	pm_runtime_set_suspended(&pdev->dev);