[SCSI] simscsi: Free scsi host on error

If scsi_add_host returned an error, the host would never be freed.
We need to call scsi_host_put() if an error happens.

Signed-off-by: Matthew Wilcox <matthew@wil.cx>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>