s390/dasd: Make setting queue_max_segments more explicit

Currently the block queue value max_segments is set to -1L, which
is then implicitly casted to unsigned short in blk_queue_max_segments.
This results in 65535 (64k) max_segments.

Even though the resulting value is correct, setting it implicitly using
-1L is rather confusing. Set the value explicitly using the USHRT_MAX
macro instead.
Reviewed-by: Stefan Haberland <sth@linux.vnet.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

drivers/s390/block/dasd.c

@@ -3140,7 +3140,7 @@ static void dasd_setup_queue(struct dasd_block *block)
 	blk_queue_logical_block_size(block->request_queue,
 				     block->bp_block);
 	blk_queue_max_hw_sectors(block->request_queue, max);
-	blk_queue_max_segments(block->request_queue, -1L);
+	blk_queue_max_segments(block->request_queue, USHRT_MAX);
 	/* with page sized segments we can translate each segement into
 	 * one idaw/tidaw
 	 */