sunvdc: kill vdc_end_request()

vdc_end_request() is a thin silly wrapper on top of
__blk_end_request().  Kill it.

[ Impact: cleanup ]

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>