spi: pic32: Don't leak DMA channels in probe error path

If the calls to devm_request_irq() or devm_spi_register_master() fail
on probe of the PIC32 SPI driver, the DMA channels requested by
pic32_spi_dma_prep() are erroneously not released.  Plug the leak.

Fixes: 1bcb9f8c ("spi: spi-pic32: Add PIC32 SPI master driver")
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Cc: <stable@vger.kernel.org> # v4.7+
Cc: Purna Chandra Mandal <purna.mandal@microchip.com>
Link: https://lore.kernel.org/r/9624250e3a7aa61274b38219a62375bac1def637.1604874488.git.lukas@wunner.deSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-pic32.c

@@ -839,6 +839,7 @@ static int pic32_spi_probe(struct platform_device *pdev)
 	return 0;
 
 err_bailout:
+	pic32_spi_dma_unprep(pic32s);
 	clk_disable_unprepare(pic32s->clk);
 err_master:
 	spi_master_put(master);