ata: ahci_st: Fix compilation warning

Remove the unused variable dev in st_ahci_probe() to avoid compilation
warning and build failures where CONFIG_WERROR is enabled.

Fixes: 3f74cd04 ("ata: libahci_platform: Parse ports-implemented property in resources getter")
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>

drivers/ata/ahci_st.c

@@ -144,7 +144,6 @@ static struct scsi_host_template ahci_platform_sht = {
 
 static int st_ahci_probe(struct platform_device *pdev)
 {
-	struct device *dev = &pdev->dev;
 	struct st_ahci_drv_data *drv_data;
 	struct ahci_host_priv *hpriv;
 	int err;