spi: spi-au1550: fix build failure

Fix a build failure introduced with commit 30670539
(spi: au1550: Fix bug in deallocation of memory)
Signed-off-by: NManuel Lauss <manuel.lauss@gmail.com>
Signed-off-by: NMark Brown <broonie@linaro.org>

drivers/spi/spi-au1550.c

@@ -945,7 +945,7 @@ static int au1550_spi_remove(struct platform_device *pdev)
 	spi_bitbang_stop(&hw->bitbang);
 	free_irq(hw->irq, hw);
 	iounmap((void __iomem *)hw->regs);
-	release_mem_region(r->start, sizeof(psc_spi_t));
+	release_mem_region(hw->ioarea->start, sizeof(psc_spi_t));
 
 	if (hw->usedma) {
 		au1550_spi_dma_rxtmp_free(hw);