staging:rts_pstor:Avoid "Bad target number" message when probing driver

Avoid "Bad LUN" and "Bad target number" message by setting the supported
max_lun and max_id for the scsi host

Signed-off-by: wwang <wei_wang@realsil.com.cn>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>