block: pass a gendisk to the queue_sysfs_entry handlers

block: pass a gendisk to the queue_sysfs_entry handlers

Despite the name in sysfs, the "queue" sysfs entries are associated
with the gendisk a that is the only block object that registers with
sysfs.  Pass the gendisk to the handlers so that we can propagate it
further in follow on patches.

Signed-off-by: Christoph Hellwig <hch@lst.de>