[SCSI] hosts.c: fixes for "no error" reported after error scenarios

This patch corrects some cases in scsi_add_host() that fail, but the "error"
return code was not reset after a prior use which set it to a non-error value.

Patch cut against scsi-rc-fixes-2.6

Signed-off-by: James Smart <james.smart@emulex.com>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>