spi: rzv2h-rspi: Fix DMA transfer error handling for signal interruption

wait_event_interruptible_timeout() can return a negative error code when
interrupted by a signal. The original code treated all non-zero return
values as success, which would incorrectly synchronize DMA channels and
return 0 instead of propagating the interruption error.

Fixes: fa08b56 ("spi: rzv2h-rspi: add support for DMA mode")
Signed-off-by: Felix Gu <ustc.gu@gmail.com>
Reviewed-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Tested-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Reviewed-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://patch.msgid.link/20260627-rspi-v1-1-170c93ee14da@gmail.com
Signed-off-by: Mark Brown <broonie@kernel.org>

Author: outman119

drivers/spi/spi-rzv2h-rspi.c

@@ -365,14 +365,14 @@ static int rzv2h_rspi_transfer_dma(struct rzv2h_rspi_priv *rspi,
 	rzv2h_rspi_clear_all_irqs(rspi);
 
 	ret = wait_event_interruptible_timeout(rspi->wait, rspi->dma_callbacked, HZ);
-	if (ret) {
+	if (ret > 0) {
 		dmaengine_synchronize(rspi->controller->dma_tx);
 		dmaengine_synchronize(rspi->controller->dma_rx);
 		ret = 0;
 	} else {
 		dmaengine_terminate_sync(rspi->controller->dma_tx);
 		dmaengine_terminate_sync(rspi->controller->dma_rx);
-		ret = -ETIMEDOUT;
+		ret = ret ?: -ETIMEDOUT;
 	}
 
 	enable_irq(rspi->irq_rx);