spi: rspi: Remove unused variable in rspi_rz_transfer_one()

Introduced by commit 8b983e90ea1a3dd82070f96c062ad521a06b7cc0 ("spi: rspi:
Extract rspi_common_transfer()"), which removed its users.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Mark Brown <broonie@linaro.org>

drivers/spi/spi-rspi.c

@@ -630,7 +630,6 @@ static int rspi_rz_transfer_one(struct spi_master *master,
 				struct spi_transfer *xfer)
 {
 	struct rspi_data *rspi = spi_master_get_devdata(master);
-	int ret;
 
 	rspi_rz_receive_init(rspi);