scsi: libsas: fix memory leak in sas_smp_get_phy_events()

We've got a memory leak with the following producer:

while true;
do cat /sys/class/sas_phy/phy-1:0:12/invalid_dword_count >/dev/null;
done

The buffer req is allocated and not freed after we return. Fix it.

Fixes: 2908d778ab3e ("[SCSI] aic94xx: new driver")
Signed-off-by: Jason Yan <yanaijie@huawei.com>
CC: John Garry <john.garry@huawei.com>
CC: chenqilin <chenqilin2@huawei.com>
CC: chenxiang <chenxiang66@hisilicon.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
static void sas_ex_disable_phy(struct domain_device *dev, int phy_id)
{
	struct expander_device *ex = &dev->ex_dev;
	struct ex_phy *phy = &ex->ex_phy[phy_id];

	sas_smp_phy_control(dev, phy_id, PHY_FUNC_DISABLE, NULL);
	phy->linkrate = SAS_PHY_DISABLED;
}

static void sas_ex_disable_phy(struct domain_device *dev, int phy_id)
{
	struct expander_device *ex = &dev->ex_dev;
	struct ex_phy *phy = &ex->ex_phy[phy_id];

	sas_smp_phy_control(dev, phy_id, PHY_FUNC_DISABLE, NULL);
	phy->linkrate = SAS_PHY_DISABLED;
}
