net: ethernet: oa_tc6: Handle failure of spi_setup

commit b3852ae upstream.

There is no guarantee that spi_setup succeed, so properly handle
the error case.

Fixes: aa58bec ("net: ethernet: oa_tc6: implement register write operation")
Signed-off-by: Stefan Wahren <wahrenst@gmx.net>
Cc: stable@kernel.org
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Link: https://patch.msgid.link/20250827115341.34608-2-wahrenst@gmx.net
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: lategoodbye

drivers/net/ethernet/oa_tc6.c

@@ -1249,7 +1249,8 @@ struct oa_tc6 *oa_tc6_init(struct spi_device *spi, struct net_device *netdev)
 
 	/* Set the SPI controller to pump at realtime priority */
 	tc6->spi->rt = true;
-	spi_setup(tc6->spi);
+	if (spi_setup(tc6->spi) < 0)
+		return NULL;
 
 	tc6->spi_ctrl_tx_buf = devm_kzalloc(&tc6->spi->dev,
 					    OA_TC6_CTRL_SPI_BUF_SIZE,