sata_mv: remove pointless NULL test

Remove !ap test, where ap is guaranteed not-NULL.  Found by way of automated
bug report from Alexander Strakh via "Linux Device Drivers Verification
Project (Svace Detector)"

Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

drivers/ata/sata_mv.c

@@ -2781,7 +2781,7 @@ static void mv_port_intr(struct ata_port *ap, u32 port_cause)
 	struct mv_port_priv *pp;
 	int edma_was_enabled;
 
-	if (!ap || (ap->flags & ATA_FLAG_DISABLED)) {
+	if (ap->flags & ATA_FLAG_DISABLED) {
 		mv_unexpected_intr(ap, 0);
 		return;
 	}