[SCSI] aic94xx: Free scsi host on error

If an error occurred during initialisation, we would sometimes fail to
call scsi_host_put() and thus end up with a leaked scsi_host.  It was
also possible to miss calling scsi_remove_host().

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