scsi: ufs-bsg: Fix runtime PM imbalance on error

scsi: ufs-bsg: Fix runtime PM imbalance on error

When ufs_bsg_alloc_desc_buffer() returns an error code, a pairing runtime
PM usage counter decrement is needed to keep the counter balanced.

Link: https://lore.kernel.org/r/20200522045932.31795-1-dinghao.liu@zju.edu.cn
Fixes: 1915ab711b91 (scsi: ufs-bsg: Wake the device before sending raw upiu commands)
Reviewed-by: Avri Altman <avri.altman@wdc.com>
Signed-off-by: Dinghao Liu <dinghao.liu@zju.edu.cn>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>