sunvdc: fix compiler warning

Stephen reports:

After merging the block tree, today's linux-next build (sparc64 defconfig)
produced this warning:

/home/sfr/next/next/drivers/block/sunvdc.c: In function 'init_queue':
/home/sfr/next/next/drivers/block/sunvdc.c:788:6: warning: unused variable 'ret' [-Wunused-variable]
  int ret;
      ^~~

Kill the unused variable.

Fixes: fa182a1f

 ("sunvdc: convert to blk-mq")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Jens Axboe <axboe@kernel.dk>