Add scsi_add_host() failure handling for aic7xxx
Also silence a compiler warning :
 drivers/scsi/aic7xxx/aic7xxx_osm.c: In function `ahc_linux_register_host':
 drivers/scsi/aic7xxx/aic7xxx_osm.c:1100: warning: ignoring return value of `scsi_add_host', declared with attribute warn_unused_result
Signed-off-by: NJesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: NJames Bottomley <James.Bottomley@SteelEye.com>