esp_scsi: remove check for ESP_MAX_TAGS

'num_tags' is an unsigned char, so the check for 'ESP_MAX_TAGS'
(which is set to 256) is pointless.

Acked-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Hannes Reinecke <hare@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>