spi: bcm2835: Tear down DMA before turning off SPI controller

On unbind of the BCM2835 SPI driver, the SPI controller is disabled
first and the DMA channels are terminated and torn down afterwards.

This seems backwards:  In the theoretical case that DMA is active,
it might try to fill the SPI FIFOs even after the controller has
been disabled.

Reverse the order, thereby mirroring what's done on ->probe().

Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://lore.kernel.org/r/ac79f1e3d6fd9a1f5e0cb4008c43b98ea70be3c2.1589557526.git.lukas@wunner.de
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-bcm2835.c

@@ -1380,14 +1380,14 @@ static int bcm2835_spi_remove(struct platform_device *pdev)
 
 	spi_unregister_controller(ctlr);
 
+	bcm2835_dma_release(ctlr, bs);
+
 	/* Clear FIFOs, and disable the HW block */
 	bcm2835_wr(bs, BCM2835_SPI_CS,
 		   BCM2835_SPI_CS_CLEAR_RX | BCM2835_SPI_CS_CLEAR_TX);
 
 	clk_disable_unprepare(bs->clk);
 
-	bcm2835_dma_release(ctlr, bs);
-
 	return 0;
 }